What's my body doing?

My fianc and I are not practicing safe sex. A day or 2 after intercourse I feel changes in my body instantly. Smells and taste r different, pulling and pinching in my uterus, sensation in breasts, hot flashes, emotions all over the place and a few seconds of pink bleeding while I peed. had this a few months ago and my test came back negative. It's happening all over again. My periods in between r normal so I don't know why my body is doing this. Please help!