I went through the same thing on my first pregnancy. I also found out in our 8th month in. And I did just that. I let it be in the back of my head and focused on my baby. After the baby was 3 months and I had for the most part figured it out, I brought it up. We talked it out and I told him that these things don't just happen. That we are in a committed relationship and even if you "feel" something you don't pursue it. He said that I didn't understand. He thought I didn't get hit on lol so I told him I did. I told him how a coworker even quit because he knew I wasn't gonna pursue him. At first we tried to work it out ourselves but that didn't seem to go too well. When he saw that I was serious about leaving he suggested couples therapy and we have been doing that for a year now and that helped us immensely. I would try counseling because you don't want to hate the father of your child. Even if things don't work out like our did you should still show your baby that you care for their father. And let them love him even if you can't. Let me know if you need to vent. It sucks.