Bleeding for almost 2.5 weeks while on the pill????

Jessenia
Hey everyone! 
I am on the birth control pill. I missed one day last month and since then (July 2) I have had a really heavy period, sometimes dark brown almost black to bright red. But it is very heavy and I have never experienced anything this heavy before and it is accompanied by cramps which I usually never have!! This kept happening even as I remembered to the rest of my pills on time. Has this ever happened to anyone else???