Why does he act like he hates me?

I was seeing this guy (I'll call him A) at uni for about a month and it was pretty intense, he'd be so sweet and kind to me and told all his friends and parents about me and everyone thought we were going to go out. Also he admitted to me he could see us together in the future, would see me every day and if he didn't see me for a few days would say he missed me and said it's crazy how he has all these feelings for me after such a short period time however he suddenly decided he wanted to just be friends as he didn't want a relationship as he'd gotten out of a 2 year one. I said that it was fine I'd be friends and we continued to be friends and still be close, the next week aswell we did a project together for our course and he was so flirty and I thought he was going to kiss me several times. He'd always message me and speak to me aswell so we were still good friends. That night I went out got really drunk and kissed a guy but he told me that A's friends told him A would kick off at him for getting with me, so I went to speak to him saying why when we're just friends. It turned into a full argument and as I was very angry I said things I regret and didn't mean, like for him to leave me alone and I want nothing to do with him. We both went home for the week after that aswell. The next day though I apologised and said I was just angry and very drunk and meant nothing of it and I was really upset about it. He said to forget about it and it's fine, even though it obviously wasn't. I got drunk a few days after and was messaging him and apologised again saying how upset I was and he assured me it was fine, he kept sending loads of messages saying not to worry or be upset that its honestly alright and to enjoy my night. After that we were alright, it wasn't back to normal but we spoke. When we got back last week we met to finish our project and we were getting on well again joking around etc but since then it's gone downhill. As the week goes on he seems to be more and more annoyed at me and I don't know why, I asked him the other day saying "we're okay aren't we?" and he ignored it. When we speak it's alright but he tried to avoid me as much as possible, usually we walk to lectures together but now he doesn't ask and just goes with someone else, who he doesn't even like. He's making it very clear he's annoyed at me and I really don't know why as it's just got worse as the weeks gone on, he makes little digs aswell about him and other girls and told me his friends get annoyed at me out but they came up to me to say hi and hug me the other night and when i asked they looked confused and said no. Also, when we were a thing his best friend would always come and say to me to trust him and his feelings are so genuine for me and he always is talking about me all the time. Why does he act like he hates me and what should I do?