Extra Period?!

So. I'm a little worried about what this means. Anyone ever had a period during your ovulation week?? My cycles are typically 33-40 days. Average is about 35 days. On Day 19 of this cycle (yesterday) I started bleeding. Turned into a full fledged period today with clots and everything. I have been testing since end of Sept with OPK and all negatives. I'm not sure why I'm having a period when it's not due until Oct 20th. I'm only on cycle day 19! We haven't BD this cycle yet so it's not implantation. Anyone had this happen?!?!