Pain? What is it? Is it normal?

So recently when my bf and I have sex certain positions hurt that didn't before. For instance when we go from missionary to me being on top, sometimes for like a slight second I get a sharp pain. I stop and then continue and it's gone. Or when he lifts my legs in missionary it'll be fine then a sharp pain one second and gone the next. It's never happened before so I'm super confused as to what it could be. It's not a consistent pain, it's just one sharp pain and then it's gone and it doesn't happen every single time.