What Causes Pain In The Pelvic Region While Having Unprotected Sex?

I'm 32 about 5'3' 125 pounds. My husband and I started trying for a baby last week. I noticed my uterus became swollen and I started to have pain in my lower pelvic region hours after trying. It has lasted for 4 days now and I am starting to feel better, but not great. Consequently, I realized that I had these same symptoms last year when I went on the pill and we started to have unprotected sex. I went through many bladder tests for IC, had an ultrasound, a MRI, etc last year. I thought it was just IC and the pill so I went off of the pill and went back to condoms. Well, the same symptoms are back after unprotected sex. Could I be allergic to his semen?