Please help!

Hey girls, I've been freaking out lately because I got my period twice this month but this second time I had what started as brown blood to a very dark red almost black color with lots of clots and its heavier by the day.. I have no idea why this is happening. I am not on any type of birth control or have had sex since my first period. If anyone has any idea of what is happening please let me know. Should I be worried?