I'm trapped in a relationship that hurts me but that person is my only support

I am going through a very complicated situation. I have an illness and I have had to return to my mother's house and leave work. Because of the illness, I have lost contact with people and the only person I practically talk to is my ex-boyfriend. The relationship hurts me but when I need support, he gives it to me. I have suffered abuse in my family so my relationship with them is not good at all. I have no one else. All I have left is the hope of getting physically well and being able to get my life back. Please help