I’m bugging out

So I wanna start by saying I really fucked up 🤦🏾‍♀️. Ok so here it goes . About 2 weeks ago I found out my in and off bf was talking to a girl he supposed to not had been with 🤔. He called her because we was having an issue and needed someone to talk to . 🤬 basically running his fucking mouth telling my business to bitches . I don’t like that shit first and foremost. I found it mad disrespectful but I agreed to get in an open relationship so I couldn’t look stupid about it right ? Wrong tho this mf was messing with her for the whole 10 months we was broken up he lived with her he was actively trying to get her pregnant he was driving her car and a gang of more shit . But let him tell it he never had sex with her he had his own place and a bunch more lies . So now I’m here hearing and seeing everything I already knew the truth too. I find out more alarming bs I care not to hear. and I see the way he is with her vs with me now I normally am a very Impulsive person and I’d been beat the hell out of both of them . But I’ve been taking a whole different approach to this situation I am now in . What you ask ? I’ve been being very distant, stand off ish and not expressing how I’m feeling. But he somehow noticed I’m not me . He keeps trying to push me to be her (friend) not gone happen at all ever . I don’t want to be in her house and I don’t want to be her friend . Honestly I’m starting to not like him too . I don’t know what I am to do because at first I tried but I am not trying anymore . He doesn’t let me out his sight . I don’t try to have sex with him anymore ( lately he has been trying to get all of us to do it together. I been taking stuff to help me sleep hard so when he touches me while they doing it I don’t hear anything and I pushes him off me . My sex drive is going down and I’m overly at peace when I’m outside with my kids alone can I please get some advice on how I can fake being happy