Swelling After Sex

My boyfriend and I don't use condoms while having sex. I have an IUD so I allow him to cum inside me. Anyway, almost immediately after we're finish my vagina swells. It also feels bruised and itchy. The itching usually goes away after cleaning up, but the pain and swelling usually lasts for 2 days. We don't have rough sex and lubrication isn't a problem, so I don't know what's going on. These symptoms have been occuing ever since we stopped using condoms. P.S. We've both been tested and we're clean