How long will he ignore me for now? What should I do?

Well me and this guy were kind of seeing each other before he got this girlfriend. He was so nice to me before they got together and we saw each other and did things together most nights. I still like him a lot and i'm quite sure he might still like me because of things that happened before this whole situation. So he got a girlfriend and then a few days later his girlfriend read texts i had sent him before they were going out. I'm guessing she got annoyed because of this as she rang and texted me telling me to stay away, but i wasn't even trying to get near. He got p*ssed off that I said she shouldn't get involved because it was before their relationship began. And since that day he has ignored me completely and basically blocked me out of his life. I still really like him and I really want him to speak to me, I can't being doing with this anymore. I've tried twice to speak to him but he just wouldn't reply. I want to try and do something or bump into him one day but it's hard because we go to different colleges. Whys he doing this? How long will he? Its been about 3 weeks now :( x