I am on birthcontrol and about three months ago I was on a gel medication that I inserted directly into my vagina, my obgyn perscribed me to it to fix the infection I had, we were unsure of the actual infection. Most likely BV. Anyway, I finished the medication and now I am just on birth control, but since the medication my past three periods have been not normal like my past ones. They are now very brown, almost black and have the consistency of jam. I haven't had any signs of actually bleeding and any of the three periods since the vaginal medication, and these periods and signs usually last for a week (7 days).
I would like to know if this is a serious problem or if it will just take time for my periods to be normal?

I am 20 by the way.