I Started Taking Adult Vitamins And An Iron Supplement As

I started taking adult vitamins and an iron supplement as well about 2 weeks ago. In the last week I noticed my stool is very dark and my period which usually only last a day or two has lasted almost a week. Could this be from to much iron in my system? The multi vitamin has 10mg and the other has 65mg, I realized this today that it is over what I am suppose to take. Could this be the cause?
Thank you