Can infertile sperm affect fertile sperm from reaching an egg? My bf is infertile but my fwb is fertile and I have unprotected sex with both.

Probably not. If you have been having unprotected sex for 6 months or more, and you are trying to get pregnant, then an evaluation of both partners is appropriate. If you are sure about the male fertility status with an adequate semen analysis, then you should be evaluated as well. Also, if you are to the point of wanting to start a family, my personal advice is to pick one partner.