Struggling with an on off ex

It was good for 5months then summer holidays came. (To clarify I'm at uni) and he had working in maga planned before me n I wasn't going to be the gf that was like no you can't go. (also by this time we were bf gf) it was planned before me so I even said we can leave it. Return in September see what happens. But he was like no still want to be with you. So he went to maga and it was hard keeping in contact. So we both mutually ended it. September came and we had been talking a bit and when we got back to uni we were seeing each other again. 

It was all good again until November when I was hardly seeing him and he was never responding. So id had enough and ended it as I felt he didn't care for me anymore. 

I tried avoiding him but Everytime we spoke he'd be like miss you. I never wanted us to end. N the odd time now n them when I was drunk I slept with him. Cause I broke up with him cause I was angry not cause I didn't still care for him. But I was trying to stay strong n not go back as he made me so happy I was terrified he'd hurt me again. (Not physically) but the pain of not having that happiness is terrible. 

So in February he finally got me to go round n talk. N I said to him I can't be sleeping with you if you're sleeping with other girls. But he told me he only wanted it to be me. Now for the rest of February we have been going great. N I have had the happiness back again. But all of a sudden he's gone cold on me from this past weekend. Not asking to meet up. Or didn't respond to me txts. Like it was in November. And I dno what to do. 

I am naturally a happy person so the fact I could feel a high increase in my happiness with him Which no one else has done is big. So now I'm so worried that maybe he doesn't want this. Or he's sleeping with another girl. Or I'm being paranoid n he's just busy. But I don't wanna be constantly txting him n badgering him if I'm not going to get a reply. HELP