I am on the pill and have been taking it as I am suppose to for 7 months stopping for one week to come on my period but this month I stopped taking my pill for a week as usual and came on my period but have been on now for 3 weeks , what is wrong?

Could be the pill... irregular bleeding sometimes happens and changing to a different one helps.
Some women develop polyps which can cause unusual bleeding... although more often in older women. Might be abnormal cells on your cervix (dysplasia)... fairly common reason.
Certainly have your doctor check it out for you.