Feel so insecure

I'm 31 weeks pregnant n feel so insecure. I feel like my bf is cheating on me while hes at work. He doesnt use social media only messenger n I have his password and I know he doesnt text any girls but idk why I feel like this. In the past he has talked to girls n when we would end things he would go to clubs n stuff but supposedly never cheated on me. N he had a drinking problem but swore to me he wouldn't drink or do cocaine and so far he hasnt. Hes changed n I hope I dont jinx it by saying that lol. But even tho he has changed I still feel like hes doing something behind my back idk what to do....