Feeling uneasy

My bf cheated on me a year ago with his ex and she got pregnant now the baby is 4 months and he's a jr. We continued to have sex off and on now I'm 4 months pregnant and idk how I feel about it..... This is my 1st child and now will be his second it's just crazy that the kids won't even be a year apart and he wants to be with me but I still have trust issues..... Idk what to do