How do you heal?

How do you heal after being cheated on? My bf just admitted he has slept with this girl twice and they have been talking a bunch. When does the heartache go away? When does the image go away???? He says he still wants to make our family work but I don’t know if I can move past this. I’ve never felt so low. And I’m 29 weeks pregnant. I could just die.. if you can relate to this, how did you move past or did you just end it? I don’t know how to let go either