it's been 45 days

Juliette
So I'm starting to get nervous because I've had my period for 45 days now and it's still going. I don't know what to do or what could be causing this.
I went to the doctor and they said that physically everything was fine and they gave me birth control that has a bunch of extreme side effects that I'm not down to have. 
Does anybody know what could cause a period to go on for 45 DAYS???! Please let me know as soon as you can.