Bleeding Alot Please Help

My doctor put me on a 10 day pill to get me too get my period cause birth control wasnt makeing me have a period and i havent had my period for a year and a half and  3 days after i stoped takeing them for the 10 days i started bleeding on 8/25 and ever since 8/26 yesterday i have been changeing my pad every 30 to 40 min cause i'm bleeding so much i'm in alot of pain with cramps and i have alot of pain in my lower back side i never use to bleed this much i'm not sure if it's cause i havent had my period in a while or should i be concerned??