Letrozole and longer period?

My periods usually last 5 or 6 days. I'm taking 5mg of letrozole this cycle to help with ovulation. (Possible PCOS, but I do have a period every month)The meds were started on day 5 of my cycle and will go through day 9. Well, today is day 8 and I'm still bleeding! It's not a lot. I'm only wearing a panty liner today (and yesterday) but it's unusual for my cycle to be this long. Could the medication be a factor?