Feeling unable to leave and accept I

I have been with my boyfriend for four years and it has always been pretty toxic but recently I feel myself becoming more and more aware of how bad it is. He is sometimes physical and violent but never really leaving a mark until recently when he punched me leaving a bruise on my arm. I also feel he may be emotionally abusive but I struggle with believing/accepting this. He is suicidal and has complicated medical problems which probably are the cause of some of his behavior. I am feeling lost and confused and am unsure if I should leave or stay and try to make it work as I have been for all this time. I love him so much and I feel it is impossible to leave and I dont want to make what hes already going through worse but at the same time I feel as if I should think about myself for once. Has anyone else experienced this? I feel to have anyone that could relate to me/ give me first hand advice I would greatly appreciate it but any advice is welcome.