Don't do flatcest

I live with 5 people, 4 of which I consider great friends so I definitely got lucky with my flatmates. That being said, I used to be good friends with the 5th flatmate in first year and some of second year too, but things took a turn for the worse. I'm not sure if flatcest was the main reason but I do believe it played a part.

Me and my friend hooked up for the first time in the first year but made it clear that we will never catch feelings and can see other people. It continued into the second year but we still had a healthy dynamic as friends and had a good time in general. It might be important to mention that he struggled to make friends in first year but in second year he got himself a big group of friends and quickly became very popular which I am happy about since it was something he complained about earlier.

However, term 2 of second year he became very cold towards me only and was the same with other people so it was definitely personal. It started from a club night when I and my other flatmate did not have a group to dance with that night so we spent some time with his friends who are not strangers and are in fact, acquaintances. But afterwards, he had a go at me for not having self-respect and said I should find my own group since it looked forced.

From then on, he has continuously taken jabs at me about my personality, saying I attract problems and am exhausting to be around, lecturing me on drinking when he drinks much more, putting me down during general knowledge quizzes in front of my flatmates by repeatedly saying I am the weak link. It got worse when he saw me with my crush at the club and told me that his friends made fun of me for hanging out with him since he's a joke in our uni (even though I like him so it shouldn't matter). He kept telling me that people think I'm impulsive and that I "downgraded" from him to my crush. I don't understand why he even needed to tell me these things.

Part of it was my fault too for always saying yes when he wanted to hook up and for being too kind to someone like him, allowing him to take me for granted. For example, when he'd get sick I would buy him groceries. In term 3, he asked me to buy him a Coke and for some reason, I couldn't find it (probably exam stress) so ended up buying him coke zero. He just started shouting at me, called me a moron, and threw it in the bin. I was too stunned to even react. I have tried confrontation in the past but he just says I can't take a joke.

I don't know what happened but I think alongside arrogance after becoming popular, flatcest really put everything to shit. I thought he was my friend but instead, his presence makes me anxious and I am now uncomfortable in my own skin. To make things worse, I am living with the same people next year. His behaviour has suppressed the fun side of my personality because I am always in fear of him shaming me for anything. I also should have stopped the hookups ages ago but hey we learn.

Don't do flatcest guys.