Annoyed beyond beliefe😡😡😡

My boyfriend has always been close with his ex girlfriend. They were together for 5 years, I got used to the fact that they were just close I guess. It bothers me a lot still though. They used to hang out all the time, that stopped after we were together about 4 or 5 months. She recently had plumbing issues at her house and she still lives at home. In the past week I have seen more of her family at our house than I would like. She came over to take a shower at our house today after I left for work. I'm pregnant with his child, I'm worried that he will start cheating on me with her like he did his other baby mom. There was no reason she couldn't come before. I'm irritated at the fact that they seem to be close again. He is a very aggresive person and I'm afraid to bring it up. He is constantly telling me the baby is not his and he doesn't want it anyway. What do i do?