Husband admitted to a FULL BODY massage with a "happy ending"?

I found out that My husband had a full body massage on Maui in a private home. He admitted to getting a HJ during a 45 minute session and paying $100. He says that was all she did to him while wearing a g-string and no top. Should I believe him when he says he ONLY did this ONCE? I have a hard time believing that it was only a HJ too. When I try to talk about this with him he gets really angry. What should I do?