Irregular menstruation

Hi!!!! This month has been a horrible month for me! My period came on 08/24 and the last day was 08/31, well that is a normal period for me! The thing is my period came back on 09/02 and it's getting worse I'm bleeding like crazy! Using tampon and pad (overnight pads) at the same time. I have to change it every hour! Someone have any idea??? I went to the doctors office on Wednesday and she said it was "normal" because I'm on birth control pills! At this time I'm feeling little weak and dizzy.