Thank you for all your replies... It's nice to know I'm not alone, although upsetting to know so many people are going through the same sort of thing. This past weekend we ended up fighting again, as per the usual format of he gets angry, I got scared and went to a friends for a bit. He got really angry when I got back because he didn't know where I'd gone, but was apparently worried? (He tried saying if I'd answered my phone he wouldn't have got mad so this whoel night was my fault) He called me a f****** c*** (I hate just typing out that

) and kept yelling at me to get in the f****** car over and over. But I felt too scared to get in with him so I didn't in the end.
I initially felt really trapped because we are living together and he's building a life here and I didn't want to put him in a difficult situation. This is less the case now, and I think the real issue now is that I don't want him to go quite yet, because I still love him and still hope we can figure it out. One of my closest friends who is aware of what's going on, most likely through her concern and care for me, makes me feel pressured to just leave... But as you say it's something that happens in it's own time.
I think he's also quite against me talking to this friend about him, and to be honest I hate to do it because I know she's my friend, she's going to look out for me and think terribly of him. But sometimes I feel like I have to talk to someone about it or I'll go crazy.
He has said a few times that I paint him out to be much worse than he is, but I suppose it would be impossible to know who's right there. Maybe it's just manipulation or maybe he really thinks his behaviours not so bad?
He did say after this weekend that he realised he probably needed help of some kind, but whether he will be proactive in getting it is different. He's two totally different people. He can be so sweet and loving, but once the switch is flipped it's like I don't know him at all.
I know his issues with me are that I don't tell him when something is wrong, but I've tried explaining to him I usually don't feel able to with him.
He has issues with me talking to male friends to, although assured him they are very much platonic friendships (I respect and love him too much to even want to flirt) and we don't talk much. This bothers me as I feel there are a few girls he is friends with that he
does flirt with, but it seems to be two sets of rules... But maybe I'm just wrong.
I always thought if someone treated you this badly it would be easier to just leave them.