e m b a r r a s s i n g !!!

I just recently started having sex and so far it's been a good time. But something that's keeping me from having a g r e a t time is whenever he's inside me I feel like I have to poop! Sometimes I'll make him stop suddenly because I'm so scared I'm going to "pass gas" (or worse oh no) which makes him confused and self conscious but the last thing I want to do is express this problem to him. I have no idea if this is normal or if there's anything I can do??