Aw hun I'm so sorry to read about what this pathetic excuse for a man has done to you and your unborn child.
Going by my past experience of this, my ex husband cheated on me while I was pregnant and even the night I had our son, he went home to her...I didn't find any of this out until my son was about 8 months old when he left her saying he wanted to make a go of it with his wife despite telling her he wanted to leave me and start a house and family with her...
Anyways, for 6 months I tried to forget about it and make it work more so for the sake of our son, I couldn't forgive him though as it wasn't so much him having sex with her it was the lies he told me and the nights he missed out on his sons development so that he could meet her that tore me up inside the most. When I look back I was a single mum from day one despite "living" with this man. So much so when I finally left him, he had to ring my friend and ask how to make up a bottle as he had never done it before.
Some people can work past adultery, and I have the biggest respect for them that they can do that. I personally can't and can't even imagine sharing a bed with a man who is or has done all that behind my back.
I was 20 years old with a 2 year old and a single mum. My ex husband was also abusive and even leaving him didn't stop him from bringing me down mentally and physically, saying no man will ever love me as I'm used goods etc, that sort of thing. It was hard and when I look back I don't know how I managed it, but when I look at what I have now, I'm so glad I didn't "settle" with him just cos he was father to my child.
I am now with my loving fiancé (who pushes my buttons but would never hurt me physically or mentally), he's been hurt and cheated on in past relationship so knows how it feels so would never do that to someone, esp the mother of his children. He took on my son as his own, gave me our daughter and now carrying his son, we have a nice home together etc.
Things seem really shit for you just now, but it's only temporary. You will get back on your feet, with or without him, cos despite what I say, u can't help who u fall in love with and if he's for you then go for it, but don't feel you "have" too due to carrying his child.
You will look back in a few months even years and it will all be a distant memory. Things will work out. But only you can make them happen sweetie and only you can make the choices.
Much love to you. It's not a nice position to be in xx