Swollen vagina after sex?

My boyfriend and I have been having sex for over a year, neither of us have an STD. And I am not allergic to latex. Recently, my vagina and everything in the vicinity has been getting swollen after sex. We don't always use condoms, I am on the pill though. But maybe it's getting swollen because of his large size and not enough lube? Because it is slightly painful and difficult to get in at times. I don't have painful urination or anything like that. It's just an uncomfortable feeling when it's swollen like that.Help!