"At least you have her back now which must be a relief"
Dear God, have you read this thread at all? It's certainly not a relief from where I'm sitting. This is a woman that dragged her DD to her ex-H(?)'s office when she needed to do uni work and who is violent towards him. I don't think it's a relief to have a child in the care of someone exhibiting violent behaviour. Do you? If the ex-H had been violent to the OP, would it be OK to leave the DD with him? There's no indication in the posts that he returned that physical violence, or that he was the originator.
"Hold on, the title of this thread is that your partner wants to shag someone at work, while you are pregnant with his second child. You are not the bad guy here. Hold onto that thought please. You aren't doing anyone any favours by whitewashing his behaviour"
And it turns out there's much more to the story (well, who knew?!). It sounds like BOTH of these people are the 'nad guys' in their treatment of each other and of their innocent child. So you, equally, aren't dointg any favours by whitewashing the OP's behaviour.
Both of them are reprehensible.
The only blameless one is the poor little girl at the centre of this. Oh, and the poor unborn child that's set to arrive into the middle of this bloody train-wreck.
One little nugget of advice - When relationships are in trouble, having a child is never, ever the answer.