brown discharge?

I have been noticing for the past few days heavy brown discharge in my underwear, I have no clue what it could possibly be and knowing me a little stressed. Then today the discharge was a lot less and a lighter brown when I went to the bathroom and wipe there was also a very small amount of blood. I am 9 days away from my period so I don't think that's the problem. I am on birth control and have missed a pill but the discharge started before the missed pill. Is there anything i should be looking out for or do you know what the cause is?