Stupid guys

Hey! 
Well I need an opinion…
I been kind of dating with a guy for the last 6 months. I'm not really sure if we are friends or we are dating
But two weeks ago I decided to have sex with him
And after that, he started to act weird and he told me that it was for the school and things like that, we don't talk like we used to and he been ignoring me 
And I feel that he just used me and I don't know what to do, like if I have to talk with him or let it go, cause I really miss him and I don't want to believe he just wanted to get into my pants…
So if anyone can give her opinion, I will appreciate it:(