I still don't understand what to.. I'm so confused.. Can someone help me please...I'll keep it short..plz?

There is this guy and he was my best friend and we dated for almost a year... He broke up with me 4 months ago and I still think about him, and miss him and cry about him everynight. He hasn't spoken to me since, and he can't even look me in the eye when we walk down the hallway. The reasoning of the breakup still confuses me, because the reason he gave me was that he didn't "want a relationship anymore" I don't understand why he would do that... he was soo happy with me. He still wears the sweatshirt I gave him though and that throws me through a loop. He hasnt spoken to me since he broke up with me and when i did confront him about the break up he honestly avoided me and tried walking away...he just kept saying over and over again he doesnt want to be in a relationship. I'm really upset because school ended and thats the last bit I have of him, I won't beable to see him anymore (from afar), I won't know his schedule or his locker combination. Next year, I totally will lose him and even in the summer will be miserable because none of my friends do anything. What should I do? Should I get him back, if so how? I'm just so confused and so lost....All answers are appreciated...Thanks:)