living with ex boyfriend, help with this nightmare?!

Me and my ex boyfriend live together at university. Rookie error, I know! We were friends when we decided to live together. One day we randomly hooked up and realised that we liked each other as more than friends. We had an amazing relationship until we started living together. It's a case of too much too soon, which is why we broke up- we started arguing too much.

I still have feelings for him but feel that maybe taking the approach "faking it until making it" is best in this scenario. As much as I'd love to still be with him, there isn't any point in telling him I still care in that way. We both started seeing other people soon after we broke up, almost to show each other and everyone else in our house how okay we were. Since we broke up I have tried to be considerate to how he may feel in my decision making, unfortunately I don't feel he has been the same. Neither of us are still seeing the new people we were seeing, but he is sleeping with another girl as a fwb (potentially with some feelings now?).

He has rubbed in my face about sleeping with other people. He will flirt with me, giving me false hope and can't stand to see me with someone other than him... but, doesn't want me anymore. The way he's treated me since we broke up hasn't been very nice and I'm fed up of moping around about it. I finally told him about him always shouting about sleeping with other girls when I am around and he claims he didn't mean to. Despite him doing this around fifty times or so...

What would you do if you were in my situation? I'm still moving on and starting to get to a good place but go back to university and living with him pretty soon. I'm in a reasonably good place but know that his games will likely impact this when I go back. I'm getting to a happier place over time but almost want to show everyone (including him) how happy I am. I feel by acting sad that it shows his games are making me feel rubbish. I also want to find coping strategies for when he insensitive and rubs other girls in my face, fed up of crying over it. Help, I'm fed up of this nightmare