What Causes Spotting And Discharge Of Brown Clumps With Blood?

Hi, I am a 25 year old female. I experienced some brown spotting a week before my 7 day break on my pill. This then turned into brown clumps mixed with blood. It was heavy for a week or so, which i assumed was my period. Now, at the end of my 7 day break, I am still experiencing the brown clumps with blood? I am getting very worried about this, as I have read that this might be a miscarraige.. please help! Thank you.