I don't understand him?

I'd been casually seeing this guy from uni for about a month, and we went very fast, he was so sweet to me always caring and showing me to his friends, he even told his parents about me etc. Everyone knew we were a thing and the way he acted around me everyone thought he really really liked me, even me as he always said it. Then very suddenly overnight he got distant and the next day claimed he just wanted to be friends. I agreed and didn't mind too much as what he was saying didn't make sense (he said he only ever saw us as friends and i interpreted it as wrong however I knew he was lying for whatever reason and it was something personal with him so didn't take it to heart) and as we really got on well and I really liked him as a person just being friends didn't bother me too much. Also I forgot to say we're in the same flat and course and are lab partners. The next few days he kind of avoided me and always messaged my friend in the flat but we all knew it was obvious he was trying to get me jealous as I acted like I didn't care as when we had to go to practicals and lectures together and got close again he stopped. We got closer as friends again but he was still flirty, and in our assessment together we did he kept getting very close and I thought he was going to kiss me several times. Later that night I went out and made out with 2 guys at the club but he was there aswell. He'd told me he didn't care and we were just mates so I thought it would be alright, I was so drunk and just having fun but his mates told one of the guys he would fight him if he got with me, so in the moment I sent him an angry text saying why does he care if we're just friends and he found me and said he doesn't care and doesn't like me then I told him to leave me alone forever. The next day I apologised and said I was very drunk didn't mean anything and he assured me it was ok and not to be upset about it. He seemed alright since then, we had both gone home for a week but we facetimed about work. When we got back we finished the assessment and we were fine getting on really well, but he did get angry at me for a stupid reason- he stormed ahead when we were walking saying i wasn't talking to him. We were fine after that but today he suddenly changed, he was very blunt when i messaged him about our test and ignored me then he walked to our lecture without me when he always asks me and we walk together so this was deliberate. If I ask him about it I know he'd just deny it so idk what to do, I'm just being his friend aswell exactly what he said he wanted, it's so obvious he seems annoyed at me and I don't know why or what to do as I really do care about him as a person and we get on so well.