In love with my ex’s best friend

This is going to be quite long so please bare with me and I know I’m going to be judged for this. I don’t know why I’m writing this maybe it’s to just get it off my chest maybe I need advice I’m not sure. I’ve been with my man for just over a year. Things went from slow to super fast and we were practically inseparable. He seemed perfect to me we were so in love but things started to happen that made me wonder about him. He’s really possessive and I noticed he would do things to try and keep me from being apart from him. We didn’t live together officially but I practically stayed at his most of the time. He lived with his mom and she treat me like family I was probably closer to her than my own mom. But he’d do things like turn off my alarm for work when I was asleep so I wouldn’t get up or put hickeys on my neck so I’d be too embarrassed to go to my modelling shoots. It was like he wanted to get me fired from my job and just keep me with him.

So he’s got this best friend, they’re super close like brothers and I hated him at first but over time I grew really fond of him. He’s so supportive, if me and my man ever had an argument he’d be the mediator and always try make things right or he’d comfort me and make me feel better about things. It was never anything romantic we became like best friends too and it was nice to have at least one person my man trusted me with. Anyway after picking up on these negatives with my man around 9 months into our relationship he picked me up from work and I told him that I felt we should go on a break. He didn’t really say anything and we drove to his so I could collect some of my things. When we got there I tried to speak to him and he just laughed which really hurt me cos it was like I’m trying to have a serious talk about the future of our relationship so I said something like “you’re a joke” maybe I shouldn’t have said it but it sent him crazy and he physically attacked me. I had to lock myself in the bathroom he was kicking the door so I climbed out of the window and ran. He’d never done anything like that before so I was hurt and shocked I couldn’t believe it. I went back home to my parents and then he started harassing me calling and texting one minute he was apologising and grovelling the next he was threatening me. I just ignored him I was done. A few weeks later I saw him with his best friend whilst I was in my car he walked over to speak to me and asked me to put the window down. I did but I said I don’t have anything to say to you. At that point he spat at me! His best friend grabbed him and I put the window back up and sped off. He came to my house that night but I didn’t let him in, then later his best friend came round and he said he just wanted to make sure I was ok. I let him in and we just spoke about things and that was the first time I’ve felt secure since any of this happened. We stayed in contact and then one night he came round and he confided in me about some things then eventually one thing led to another and we slept together. I know I’ll be judged but I don’t regret it at all I feel like I’m in love with him. He told me how he feels about me he said he was willing to take the risk but then a few days later he started acting off with me and then he said he can’t do it to his friend and it didn’t really mean anything we were both just upset! I could tell he didn’t mean what he was saying he wouldn’t even look me in the eye! Fast forward now my ex/boyfriend’s mom was in a really bad car accident and his best friend called me and asked me to come to the hospital. I went and I was so heartbroken for everyone but I still had made my mind up that I didn’t want to get back with my ex and thought it was best to just be rid of both of them, but then she passed away and everyone was saying I can’t leave my ex now cos he needs me. So we’re sort of back together. It’s been like a month or so and things have been ok but I don’t want to be with him but I feel so guilty I’m scared of what he’ll do if I leave. He doesn’t know what happened between me and his friend. I think it would send him over the edge but I feel like his friend is who I want to be with. I haven’t pursued him any further since he told me he didn’t want to but I just feel so lost I don’t know what to do