How long for period to be normal

Brittany
How long after you had your baby did it take for your period to be normal again? My son will be 7 months in two days and I pretty much have 2 periods a month. I have been on the pill since my 6 week check up. Last month I thought I was back to normal, but now I'm on period but its not time for it. Any other mommies have/had this problem??