It was on September 19 2009 when I proposed her and our relationship began.. I was our first year in University.. there after we were having very good relationship.. I was Student Council Member and became President for the last year in the college.. we enjoyed a good reputation as a very good couple in the college.. During that time she use to get very angry on various issues and I use to settle everything with great efforts. She use to say that.. she would die if I won't marry her. Every one in college knew us as a very good couple and even Professors use to ask us to invite them to the marriage.
We use to plan our entire life.. the car.. the house.. our kids.. and even their marriage. After the college ended.. she started working in a company.. and me too in a different company.. we were in same city.. and we use to meet there as well.. but not as much as we use to meet at college.. and it continued for 6 -7 months.. starting from January 2012..

She introduced me to her new work mates.. and everything was fine.. but one day she said that some of the guys and girls from her company is coming to see her when we were at a shopping mall.. and she asked me that we will pretend as just friends in front of these people.. I was stunned.. but just ignored it.. in the month of April 2012 one day when we were just kidding... I opened her inbox (mobile phone) in front of her to show her a message that I sent her last night . But in her inbox I found some texts from one of the guy from same group.. and she said that he is after her and there is nothing like that.. I again trusted her.. and after that nothing happened.. on June 9 2012 I came back my home town for a kind of emergency at my place.. and we use to talk over phone.. most of the time she use to ignore my calls and all that happened.. she said that she is a little busy with her work. On July 18 onward she stopped picking up phone call s and stopped replying.. my texts.. and even told our mutual friends that she don't want to talk about me.. on August 9 2012 it was my birthday . She didn't even bothered to call me or even text me.. on 12 I called her cell back to back.. but she only text me and said that she don't like me any more and want freedom from me.. and reason that she gave.. was that her dad don't want her to continue the relationship.
I had the password to her email id and when I checked her sent items.. I found out that she is having a relation form one of her work mates who was never in picture earlier and in the mail she promised him every thing same she use to promise me.. she even blocked me on Facebook.

What should I do now.. and why she did this.. everyone in my college use to say that I loved her more than usual... I use to care for her a lot..! I don't understand what to do..?

She has moved on with her life. Your relationship was while you were in college. When she went out into the working world she met someone. Your clue was when she told you to act like you were just friends. She didn't handle it correctly, and should have broken up with you. Either way, it's time for you to move on with your life.

You have to do what millions of us do when we are dumped - you fill your days and nights with as much distraction as possible with friends, studies, work, hobbies, sports, walking, movies, music, reading, animals - whatever it takes to kill the pain.
There's no point in looking back at how perfect you were once, or how other people thought you were the couple whose wedding they wanted to go to, or how much you loved her - she no longer has feelings for you. Yes, it hurts! That's life.

I need your advice on this sir! This is what I know but not able to accept.. the memories are killing me.. Knowing that she is sleeping with some one in no time and at the same time knowing that the other guy is using her.. Can't take her out of my mind. She is stuck in there.. Its really painful..!

Move on bro, you have nothing more to gain from this girl. When she asked you to pretend like you were friends in front of her colleagues, she took all of your pride with it. That is just bad
It looks like she's discovered an outer world that intrigues her and that she wants to explore further. She'll understand later on what she has left behind