Incapable of leaving unhappy relationship

I’ve (27F) been dating my current boyfriend (almost 33M) for a year. We have dated before and broke up 2 years prior getting back together. It was my first relationship back then and first sexual experience as well. I was quite in love but few months into us seeing each other he told me that he actually doesn’t want relationship with me but I was already very much in love and stayed with him and he wasn’t treating me very well even though it was him who initiated us getting together back then. We were dating also a little bit over a year back then. I was quite devastated after the break up (first time Ive tried psychotherapy) and was living in a haze for the next half a year, getting over it, then it got little bit better but I was still thinking about how he treated me from time to time and it definitely affected how I dated after.

Ive dated few people in the meantime, more of the bad experiences than good ones but there were good. Then approximately something little bit over year and half after the break up I met this guy from Bumble and I fell in love very hard but then it ended up catastrophically and I was quite devastated from it as well. I travelled abroad to get over it and met my ex (now again current) boyfriend there. We talked a bit and I confided in him about my experiences dating after we broke up (we were little bit in touch before, like texting maybe every few months about something small, but I wasnt into him romantically anymore). Anyway the experiences Ive shared were quite traumatic and seeking comfort I slept with him during that time (it was me initiating it). We have spent like 3 weeks together before he left and I stayed a month longer abroad. During the time we were together abroad I got annoyed by him many times and we already argued and even though we have spent that whole time together I saw it nothing more but a fling and that maybe we could stay friends once I come back home.

Well, he called me few times, saying he wants a relationship now and somehow got the idea that we should get back together which I was quite unsure of but he was giving me ultimatums like if Im not dating him then we cannot see each other as friends. I was still vulnerable from the break up with the previous guy and getting over it, we had few calls where he stressed me to the point of crying and calling me a wh**e for having the same body count as him that I managed to get in 2 years and he was getting to it in longer time (still dont believe him). Anyway, I was unsure and getting back together with him felt like doing something out of fear so I was quite sure that nothing would happen, if anything I had this selfish idea that maybe we can date a little bit and he could make up for some of the bad things he had done to me before and then we could go our separate ways.

Well, he picked me up from the airport after Ive came back and its been a year … we managed to travel for half a year together throughout Asia and we had so many arguments over such a small things. I think we are just incompatible and also my sister thinks he is narcissist (he was her university friend for a few years before I met him and they’ve known each other quite well). I know what I should do because I dont feel much for him anymore and Im not really physically attracted to him anymore and there are many things about him that annoys me, at the same time I feel like there is some connection between us but more like me being sad for him for being alone again if that makes sense (his whole family lives in a different country), I think that part of me that still likes him sees him more as a child to take care of than as a partner. Other reasons Im having doubts or Im trying to postpone it even though I know what I have to do are that we already moved in together and it is hard to get an apartment in our city and also we started a project together with other people that Ive been working on for half a year for free and I was supposed to get shares in the company that Im not sure I will get anything from now (which I still wouldnt stay for in not functional relationship). And one thing, Im scared of being alone again. Alone in my apartment, alone without any meaningful connections. I have close friends in the city and my sister as well but they cannot be with me all the time.

Basically I know what I have to do but I feel like my life is crumbling in between my fingers and I know it has to happen, Im just gathering the courage and I guess I need to hear some words from strangers even though my friends and my sister already know about this. I haven’t written much of the reasons why I think we are incompatible but lets say there are many clashes in personality. The main thing though is that I think Ive never forgiven him the betrayal from the first relationship even though Ive tried.

TLDR: Im unhappy in a relationship with a guy Ive dated before and who treated me bad back then but got back together somehow “accidentally” after few years. The relationship started little bit weird again and its been a year, I know I have to end it Im just too scared for my life to fall apart again.