Is he cheating?

My boyfriend and I have been together for almost three years. We broke up for two months and in those two months he has sex with two other girls. Once he was ready to commit again we got back together. We’ve been back together for over six months now with our relationship better than ever before. I’m currently 22 weeks pregnant with his baby. His coworker texted me the other day saying that she heard he was having sex with another female they work with. The girl who texted me used to be my friend but we just slowly lost contact over the years. My boyfriend has been texting the girl that he was accused to have sex with. When I heard I asked him and he told me it wasn’t true and he wouldn’t ever hurt me. He immediately blocked her once I asked and promised me he wouldn’t ever talk to her again. I believe him, although part of me is also nervous. I don’t think he would have done anything like that, but I thought it was random that she went out of her way to communicate to me that she heard that.. any advice?

Thank you in advance