HELP???

About 3 weeks ago I had protected sex and realized after I was bleeding bright red and there was some blood on the condom too. The bleeding was only enough to notice when I wiped but not ongoing. My period started two weeks later and was extremely heavy unlike it has been for years. My period stopped Wednesday and I had sex early Friday morning and started bleeding again. After that, I started passing blood clots like my period was back and heavy again however that stopped and last night I had unprotected sex with no bleeding at all and unprotected again this morning with no bleeding. But I have been extremely nauseous and lightheaded ever since & when I went to bathroom just now noticed bright red blood again when I wiped. Any ideas what’s causing this???