4dpo guesstimate

Vanessa
I took an ovulation test on Sunday and it came out positive ...I had 3 fertile days before that according to one of my apps. I bd on all the days..now I'm 4dpo with bad nauseous feeling...cramps..back pain..my periods are super irregular and af isn't due till prolly March..what could it be? Been ttc since November (had Mc Nov 15)