How To Tell Your 4 Years Bf That Ur Sex Is Getting Lame ??

So I have a boyfriend and we're already 4 years. We all know that sex is hot, fun and all that in the beginning of the relationship, but I am starting to get bored with our rounds :(( I love him, I really do. And I don't think of leaving him just bc our sex is getting lame. I feel really sad because we can go 4 rounds without me cumming and I don't know if he doesn't mind or he just doesn't know. We just finished a while ago and im dry af