I know this question has been asked numerous times..But none with my specifics

for my last two periods..I have been getting a reddish brownish blackish discharge instead of my normal periods...I will have no signs of cramps or anything that deals with my period...But instead will have a very light normal period the first day...And then get the same red brown black discharge...Sometimes it can be clumpy...And other times it appears like a liquid..I am not on birth control and I am a virgin...Anybody have any ideas what this could be? Thanks for the help....