Wow, just wow. I honestly can't imagine how you are feeling and have never experienced anything like this but:
Please, please go and get checked out somehow. Can you call 111 and explain you don't have transport? If you say how heavily pregnant you are and describe what happened they might send someone to either look after you at home or transport you to the nearest hospital. Or can you take a taxi? (sorry maybe I missed something above and know that's expensive)
Also please, please report him. For several reasons. This is DV. The police are very used to dealing with cases like this, I think it's highly unlikely they'll accept him saying you are a psycho. Also the marks (if they are still there) clearly match your story of defending yourself. You are obviously and understandably very shaken, they will have someone you can talk to in confidence (e.g. Women's Aid). The way he has behaved, especially showing no remorse afterwards - shows no respect for you. You are carrying his child and very heavily pregnant, and no matter how much you were arguing he was wrong to lay a finger on you, it's beyond wrong. Also, if he has done it once (and you do nothing) what if he does it again? At least if you get the incident recorded, if he does do it again that will shows the police / SS a pattern. You could also show them this thread.
Perhaps ask yourself whether you can live without reporting it (and possibly also without any remorse or apology). Are you ok with your children seeing the way you are being treated, and respond to that, and learning that that is the 'norm' - that that is the way to treat a woman / be treated by a man?
Think of it from the point of view of your OH - he has attacked the mother of his child, who is heavily pregnant, then gone to sleep soundly, then got up and gone to work as though he did nothing wrong. Is that ok behaviour? You have a right to be very angry and he is the one who should be scared.
Know that abusers (and that's what he is, in this situation) always make their victims feel like they are in the wrong, make them doubt themselves, make them feel they won't be believed etc. And often apologise and put on their best behaviour for a while afterwards, only to do the same thing again, and again. I know it's hard but you are a mother already and about to have another child, and you are making complete sense whether you think so or not.