Cheating while pregnant

So almost a month ago (May 3rd) I found out my partner was cheating on me with a coworker. (She knew about me) He said they had sex 3 times, hung out twice while I was visiting my mom when he was suppose to be doing something else. And obviously at work seeing each other each day. He said it was exciting and feels like we don’t have that spark like we used to, and he started getting feelings for her.

We have a 18 month old and I am currently 27 weeks pregnant. We own a home. I am 25 he will be 27. we are not married but have been Together for almost 4 years. I’m a stay at home mom but still pay half the mortgage and my own bills. Plus some groceries. So I’m not fully dependent on him.

He claims he did it because we were not having sex during this pregnancy and he wasn’t overall happy. (We did fight a lot but i do most the house work and taking care of our daughter. He spends lots of money on his car, golfs every Tuesday and hockey every Friday. Most Saturday or Sunday is at a car show.) so i get upset and probably more defensive then i should when we argue over things but I’m exhausted and feel alone 24/7.

pregnancy sex hurts for me and I’ve been High Risk with an unknown heart condition, being put on medication and being so worn out in the beginning few months and chasing a young toddler.

So he had sex with me, then her, then me, then her and her again supposedly. All with no condoms. I made us both get tested and all came back negative thank god.

I guess I’m wondering if anyone WITH kids has stayed and tried to work their relationship out, or if you just had the strength to leave. Part of me wants to work it out with him, but part of me knows I don’t deserve that BS.

I already know he’s f*cked up, so just a bunch of negative comments won’t help what i already know. I’m looking for feedback from those who have experienced infidelity or betrayal.

we are trying therapy for the last few weeks as he says he would like to work it out and if he wanted to leave he would have when I have him the chance.. I’m just so lost and confused and devastated.