Is this normal,not implantation

Zee

I stopped tracking with opks and I have had cramps since Sunday night and started spotting on Monday morning. It turned into almost a full on period. It isn’t implantation since it’s too dark and has clots. Through the 8-14 my af was on and off throughout the day for longer than usual(af usually last 4-5 days for me). Does anyone know what’s happening or had this before? Ovulation day was “supposed” to be around this time.