Help!

So I'm having this problem
My boyfriend and I met a while ago
When we first started having sex it was great! No problems at all
Now when we try to have sex my vagina is doing some kind of weird "gripping" thing close to the entrance and it's making sex very painful. 
And I know I'm wet enough for sure and sometimes just in case we use lube as well. I don't know what it is
But it's effecting our relationship. And It's a problem