Could My Husband be Possibly Cheating

My husband are expecting our second child, a boy and I'm currently I'm 27 weeks pregnant. He has been distant lately and hasn't shown much affection. We haven't had sex in a couple of weeks and when I ask him if he wants to he tells me he is not in the mood or is tired. He has been going off a lot more lately and is very private about his phone. I know he has a new female friend, she is much younger. I don't mind him having female friends, but I have yet to meet this new one. I feel jealous, insecure, and uncertain if he wants to continue our marriage. He tells me he is not having an affair and that I'm the only one for him, but right now I feel like I don't matter to him. I want him to spend more time with me and our daughter, but he just tells me to leave him alone. Right now he is not in bed and did not tell me where he was going. I just don't know what to do anymore.

Edit: We had sex last night and had anal sex for the first time. Not sure if I like it. Even after that he left the room to talk and text on his phone. I know something is wrong, but he will not tell me. He says he is talking to others about what is going on. He says his issue has nothing to do with me. He told me not to bring it up again. However, his distant and suspicious behavior does not help my insecurities. I know he has a stressful job as a firefighter and the fact he is the only one working. Plus his brother who has been told he can't move in his new gf and her kid has been trying to. By the way he has 3 kids of his own that my husband and I and his parents took care of during his incarceration. It's a mess around our house, but my husband works 24 hrs off 48 hr, plus has two part-time jobs, so he doesn't have to deal with most of the crap around here. But I don't think that is what is bothering him. I just wish he would open up to me.