Pregnant and cheating

I’m 23 weeks pregnant and i’ve recently looked through one of my boyfriends phones. I found that he’s been talking to other girls and even go out to see them. From the text messages i’ve seen that he gave oral sex to one of the girls and it’s probably been multiple times he’s done it. I haven’t had sex with him lately, simply because i don’t feel like it. I’m trying to figure out how to confront him.