Can I get him back?!?

So I have this major crush on one of my guy friends... in the beginning of the school year i got to a point with him to which we'd act like we were going out, at this point i knew for sure that he liked me, then starting the new year i started to become really busy and i stopped hanging with him as much... but even though I stopped hanging with him i still feel the same way as before but he doesn't even talk to me!! To add on to that he has a girlfriend and i had to figure this out from another friend!! How can i get him back, or at least our friendship...