Done messed up😪

So....me and SO had intercourse new year eve/day w.e. anyways AF showed up next day and was normal....for the first two days. Then it went to spotting and then nothing on the fourth. Not normal. I figured that since AF was due the next day all would be a ok.....i might have been wrong (I hope not). So for the past 24 hours i have been cramping on and off. Had a spec or two of pink blood. I took an opk to see if it was ovulation cramps it came back negative.

Anyway i couldve concieved the day before AF showed?