Cheating and confused

So I’m 6 1/2 months pregnant. I found out my husband was texting another woman that he was in basic training with. I thought it was odd when I found out at first and told him I didn’t like it. Well tonight I seen texts between them both and he was practically begging her for naked pictures. She did not send anything, and she actually told him no many times. But he still kept asking for them. He said that he needs “strange” sometimes because the normal gets boring. We haven’t been able to have sex because they thought I had placenta previa, so it’s been about 2 months since we’ve had sex. I’m not sure what to do. I don’t even care that he did this to me, more the fact that he did it to our unborn son. I’m confused as what to do. Obviously if we weren’t together, I would end it in a heartbeat. But now I have someone to think about other than me, other than us. Just looking for advice.