Anxious and afraid

I have terrible anxiety and can't seem to shake it. My boyfriend just left today for a week for a "guys" trip (his best friend, his dad and his dads best friend) his dad and his dads best friend drove down to Nevada. My boyfriend and his best friend flew down today. They are planning on staying around the Vegas area. All I can think of is how people cheat when they're down there and how "what happens in Vegas stays in Vegas". I'm so afraid that this is going to be the truth. I've been struggling it's creating so much resentment. I'm not sure how to talk to him what's okay what's not and I'm constantly almost on a nervous break down today.