excessive bleeding, input please!!!!

So I had my little guy 11 weeks ago (12 weeks this upcoming Wednesday) and I had my first period already. It started December 22nd and ended January 6th (doctor said it was okay even though it last 16 days) well I was due to start my next one this past Friday which was the 20th and I did, I am on day 3 now and I am bleeding  Excessively!!!! I'm talking bleeding out of a regular size tampon every hour sometimes not even making it an hour (yes I do plan to buy  super plus or ultra size tampons today) but does that seem normal? To bleed out of a tampon in an hour or just under and hour? Should I call my doctor? I woke up every hour last night to change it and it's still the same way this morning. Please help!