Spiralling with no control.

So I'm just looking for some advice. My partner and I had been together for 3 years and a few months ago he cheated on me with his ex girlfriend but I was still willing to work things out with him until 1 week later he broke up with me and I left the house we both shared and went to stay with my sister. Throughout the time we havnt been together he hasn't been very nice to me calling me names and just having a disgusting attitude with me.. He went out of his way to tell me that he had sex with someone else and I also know that he was going and visiting his ex girlfriend, in the end I just left him alone and starting concentrating on myself and I went on a few dates with a guy who is really lovely in every way but after meeting up with him a few times my ex started messaging me again still saying he didn't want to get back with me until I told him that I was dating someone which I admit I did tell him because I wanted to get at hi abit but after that he started going crazy trying to find out who this guy was and told me I wasn't allowed to see anyone and then he decided he did want to be with me again so I wasn't allowed to speak to anyone else or he would beat them up, he's abit of a crazy person when it comes to fighting and iod my want this poor guy to be hurt because of me so I stopped talking to him and then my ex would talk to me constantly like we was together he tells me he loves me and I say it back but I do t know if I mean it anymore, I feel like I have no control over my life he tells people we are back together even though I tell him we are not and now he has just moved himself into my sisters with me and is saving for us to have our own place again and he keeps telling me all this stuff we are doing and I feel like I can't say anything because I don't know what his reaction would be or if he would even pay any attention to it and I don't want him to be upset which is stupid I know but now I feel like I'm going crazy, I used to be such a different person before we ever got together and now I feel like nothing I can't talk to people I now have no confidence as he has a very big personality it was always difficult to be myself and now I've lost myself. I feel like I'm going to be stuck being unhappy forever and I just keep thinking how I could of been happy with the other guy and how he would of treated me nice and like an equal. I don't know what to do and would like to know if anyone has been in similar situations and how they got out of them.