Is Pregnancy Possible Through Intercourse Four Days After Menstruation?

I started on the patch over a month ago. I was on it for the 3 weeks fresh patch each week, and last week patch-free which then I had my painful period. I then forgot to put the patch on the new week after my period finished... I had unprotected sex 4 days after and around 10 days later having this heavy brown/black flow 2 weeks early to when my next periods due? Could I be pregnant or is it just hormonal unbalance? Thank you for reading.