Why doesn't my boyfriend communicate anymore?

I have been dating my wonderful bf for 4 and a half years now. everything between us was amazing until about a year ago we started to get a little rocky. we are in college so school is a pretty important thing to both of us, like it should be for anyone right? well all of my girlfriends that have boyfriends see them on a normal basis and they are in school as well. but my bf all of a sudden stopped coming over as much and stopped wanting to hang out. so when i confronted him he gets all mad and says that right now school is more important than me. i understand that school is important but why does he have to make it clear to me that its more important than our relationship? its not just this issue, its stuff like he never wants to talk about a problem if we have one. i bring it up to tell him im upset and he tells me im being a cry baby and i just like starting fights. when thats the last thing i want to do is fight. i know guys dont like talking and stuff but i have been with him for almost 5 years and he used to not be like this. i confronted him about if maybe he is tired of me and wants to move on but he just denies it says e loves me and to stop dragging things out. its so bad to the point where im crying all the time and its pushing me away. i love him very much and i want this to work. can anyone help me with why he is shutting me off like this?? its driving me nuts!
thank you for answering and giving me your opinions. i was thinking that maybe his spark is gone for me. but why would he deny it when i ask him? and why would he stay with me if he didnt want it anymore?