Spotting or something else?

Me

So, I last had unprotected sex on September 24, the last day of my period. Since then I’ve felt off/on nausea, and the third day after I had major cramps to point it was hard to walk. Since then been normal, but had sex yet again on the 13th. Yesterday, I wiped and had light reddish pink spots, and since then nothing. I’m not supposed to get my period for 3 days.. and I’m not on any birth control if that makes any difference. What could this mean?