excessive blood

Okay ladies I'd like to know opinions or if you have experienced the same thing. I'm on the depo provera and I haven't had a period in about 2 months (I've been on this for almost a year) I started bleeding so heavy, very heavy. Abd by heavy I mean my underwear was soaked in blood in under a minute. This happened randomly abd obviously happened very fast. I am sexually active. I was wondering if any of you ladies have gotten this and/or what you think it could be ?