Emotionally abusive relationship?? I'm stuck..?

I just can't get myself out of an emotionally abusive relationship. I'm battling with depression right now and my ex takes advantage of it he knows I'm mentally weak, he'll put me down, blame our problems on me. I know I'm in danger but its so hard I feel so alone and feel I need him. An example of his behavior, I walked all the way to his house at 3am I don't remember why but he snapped on me, I was on the floor crying. My crying bothered him so he threw a water bottle at me, I still kept crying so he threatned to drag me by my hair to the room next door. I cried for him to walk me upstairs or put the dogs away so I could go home but he threatned to have the dogs bite me if I tried going home. Not only that he tries to force me to do sexual things I don't want to do, when I don't do them we fight terriblly. I also know he's cheating on me I feel and sound so stupid writting all this, I know I need to leave but I just can't, any advice on how to get the courage and strength to just leave?