Confusion

What do you do when you love someone soo much that even though you know deep down in your mind that you shouldn't be with that person. When you know that this person has hurt you in the past but you keep running back to them. We fight alot, I cry alot .. But for some reason as much as I don't want to I always end up back in his arms. I don't know what it is about him, he just has a special way of getting to me. My heart sinks when he tells me about how much he loves me and cares about me. So what do I do when it seems almost impossible to live without him ?