HELP!!

I started birth control a month ago and Ive been bleeding for 2 weeks now. Ive been bleeding through Super tampons, alot of blood clots and big ones, also passing big chunks of tissue and excruciating cramps. Blood literally pouring down my legs and leaving a trail to the bathroom. I usually have a pretty heavy flow without birth control for like 2 days but ive never bled through tampons so this is definitely alot of blood to me. Is this normal??