Period or inplantation bleeding?

Elizabeth
The day before my period was do i started to bleex heavy dark and clotty blood it only lasted that one day nothing else. Havent had sex since ovulation on CD 15-17 i take clomid on cd 3-7. Could this be inplantation bleeding? Had a miscarriage at 8 weeks july 2. I do have a healthy 2 year old. I also have PCOS