Feeling like a bad person

Needing some advice or encouragement.... my boyfriend and I have been together for 2 years now. I wanted a baby so badly so we had one but unfortunately she got very sick unexpectedly and ended up passing away. It’s been a few months since her passing and I am dying for another baby. I will do anything to have another baby to give all this love to. My boyfriend has cheated on me quite a few times in this relationship and I’m fed up but I want a baby so badly that I’m starting to have bad thoughts of getting pregnant first and then leaving him... still raising the baby together because he’s an amazing dad. Even if he didn’t want the baby, I’d be a happy single mother because that’s how bad I want this. It’s just that if I don’t have a baby with him, i won’t find another man for quite awhile to have one and adoption takes way too long and I want my own child