Most Helpful Guy
I don't know exactly what the situation was, but sometimes when your with someone who always keeps you on edge you get used to the constant stress. You become accustomed to it then when its gone, you miss that feeling however messed up it was. Just based on what you put in your overall question, how he discarded you like yesterdays garbage and doesn't acknowledge your presence and went back to the lifestyle he supposedly despised, he probably has a personality disorder. These people have a way of screwing with your head like no other. Either way you mentioned you were in college which is awesome, concentrate on making yourself the best you can be. Set goals for yourself and don't rest until you meet those goals, then set even higher goals.
It will take time, but the pain and confusion caused by this loser will subside. Redirect those negative feelings into motivation to rise to the top of whatever you choose to be.