Chippy is bang on with the Samaritans. I've called them myself, and it's great, because you can spill everything out, and have a good cry, and they're there to listen and offer advice but they don't judge. And you don't have to worry about what they think like you might a friend, because they don't know who you are.
Talk to your GP too, and see if you can get a referral for a counsellor - they might be able to fast track you if you're pregnant and mention that you've cut yourself. Please don't hurt yourself again though - he isn't worth you causing yourself any more pain on top of the rest. If you're feeling low, try opening a word docment and writing a long, expletive-filled letter - or write it by hand. I do that when things get me down, and it's great to just yell at the paper and tell it all the things going through your head. Afterward, you can delete it, keep it, or print it out and rip it into shreds. But it's a good way to get some of the anger and hurt out of your system, and by the end you feel tired but better, for a while at least.
And don't forget your little one. It's in there, getting stronger each day. You'll have a scan soon, right? Try and focus on the new person in your life rather than the old. It's a much more positive feeling, and anything which distracts you from the pain you're in right now has got to be a good thing.