Why is it that you realize you love your ex so much when his already with someone else??

I thought about it for weeks and now i came to realize that I just cannot hate him or get angry with Him because he has fallen for someone else... Why?? simple because back in college when we broke up march 2009, after my OJT he contacted me and I told him bluntly that the relationship cannot be fix because i've completely fallen out of love with him. Inside 2years and 5months when we were separated from each other after our break-up he never gave up on me, and everytime I kept reminding him of how much i've fallen out of love with him as in totally i have no more feelings for Him he never turned bitter on Me. He never got angry with Me or even tried replacing me despite my bluntness with him...He knows the painful things that i'm doing where i think other guys will find it hard to accept if they were on his shoes. BUT he never left and never turned bitter on me despite everything that i've done when were apart. He still remained a friend to me despite everything.
THIS TIME...after thinking a lot, I actually understand why he has fallen..he is undergoing the common phase that most people undergo after break-up..battling your weakness and vulnerability...You will give-in if you are spiritually weak, BUT you can survive on your own "Alone" if you can keep a strong spirit and rational mind while dealing with mix emotions in trying to surpass the pain caused by break-up..
{{IF YOU ARE UGLY or your partner is so ugly, DON'T WORRY too much..only few people will attempt to take advantage of the person's vulnerability, that is if his not the one making a move to move on from the relationship..(just kidding ;) hehe....}}
WHAT HAPPENED to our relationship??... i broke up with Him and he felt down..then a girl notice how down he is so this girl started approaching Him and started consoling Him (mined you, His not ugly and his now a manger in a particular area of that company so ofcourse He is now attractive to other women inside that company)... in my absence this girl kept approaching Him and cared for him when he is down, and because of that care He started opening up about the problems we had in our relationship and the girl is giving him advices on how to get over me easily. He felt comfort out of the girl's presence and slowly he developed feelings for her.... While Me on the other hand was hoping he'll learn and do something about what's wrong with our relationship and why i have to end it... BUT the opposite happened.. I discovered his starting to have feelings for someone else, the one who generously lend him her shoulders for him to lean on when were apart...until finally his feelings are no longer mine anymore... and because of that I felt tremendous pain. I thought I'm not really inlove with Him before because when we used to be together i can still think of someone else..but when i discovered his falling for someone else I realize how painful it is to know that he has finally got over me because his feelings are no longer mine... Reading how he is hurting from someone else on his wall is not so easy to take.. BUT i cannot hate Him, I cannot be bitter with Him.. i tried ranting to myself about his bad sides BUT it's not enough to make me hate Him...simply because no matter how much i'll think about his wrong doings, THE good side in him that he has shown to me before when we first broke-up on how he was taking it without thoughts of replacing me is dominating in my mind more than the reason why i'm feeling this tremendous pain now, which is caused by Him having feelings for someone else. I cannot hate Him because he never once hated me inside 2years and 5months of our break-up.. I cannot be bitter with him because he was never bitter with me inside 2years and 5months of our break-up.. He never left me as a friend despite knowing I'm NOT inlove with him anymore inside those years, and the fact that he knows the things i've been doing which isn't good those times when were apart... He waited for Me.. Everytime i'm breaking up with someone else those times He kept coming back to me, to ask me If he can again be my boyfriend, BUT I always turned Him down, telling him i have no more feelings for Him. BUT still He remained my friend despite my bluntness to him. Until finally after 2years and 5months of our break up I gave him a chance....and that's why we got back together.
So...if i'll only think about my own feelings now on how hurt I am because his falling for someone else, that will be too selfish of Me because those times when i was having feelings for someone else He never left Me as a friend.
Anyway, a relationship is composed of two things Happy days and Bad days...why is there a need for me to think too much of the bad days when actually in our whole relationship those bad days are only small portions of the whole relationship?!...in my mind i am fighting my own thoughts..I shouldn't let pain dominate me more coz that will lead me to focus only on the bad side instead of thinking also about the good side that mostly composed our relationship.
Anyway, CURRENTLY we are friends.. the other girl has turn cold on him because she is confuse if he still got feelings for me or not because until now he hasn't change his status or remove my pictures on his profile. She even asked him why he is seeing me last time when we shouldn't be seeing each other anymore because we already broke up..it's more like we shouldn't be friends because we already broke up....the girl doesn't feel secure with his feelings for her. So the girl made a move to get over him by turning cold and being with someone else infront of Him. And seeing the other girl with someone else brings him pain which became the reason why in his wall he is suffering... As a friend, i am obliged to give him a more rational advice instead of a selfish one even if it means my own advice will hurt me... I told him "i'll give way coz i'm his ex..if He likes her it will be hard for him to convince her that he is no longer inlove with me if he is still friends with me and his profile still got pictures of Me, plus the fact that it is still in a relationship with me in his profile".
He is currently battling between the commitment he made with me and the feelings he now has for someone else that's why he doesn't wanna remove our photos...
AND ME on the other hand doesn't like competition. If someone wants my guy, i will give way if he has fallen for that someone, because i don't wanna keep Him by my side if He is no longer inlove with me because that would mean being with me won't be able to make him Happy anymore...BUT i can be a friend to Him if his not with someone else... I told Him to let go of our friendship because i'm his ex, it is not healthy to keep me as a friend if he wants his new interest to feel secure with him. But He doesn't want to let go, instead He told me if She can't understand our friendship then it's better if he won't continue pursuing her at all, instead he'll try to forget his feelings for her because his next GF should be able to understand that part. The part where Me and Him are still friends despite the break-up.
ANYWAY, eventhough it's somewhat heart melting to know his choosing our friendship instead of this new girl that he likes.. I'm not really holding on to his words and keep-in-mind that He can keep it... Because in this world, A lot could happen.. If you'll say something now, what you say now might change later due to mix emotions and undergoing different pressures of different situations that can caused alterations on how you meant it last time when you said it and how you'll feel after surpassing all of those pressures and circumstances that will take part on the coming days that hasn't pass yet...which can make you forget the used-to-be feeling when you said it. 
AGAIN: A lot could happen...so what is being said now might change when being thrown a lot of different situations and circumstances that can cause alterations in a person's state of mind and heart.