What Causes Brownish Discharge During Menstruation?

hello i had a baby 4 months and 1 week ago and i had finished bleeding after 2 weeks , i went on to the contraceptive patch evria i think that is how it is spelt and i started bleeding like a brownish blood but the amount of a period so i thought that my body had not excepted the patch after i had the baby so i went to my docters and had swabs done and the result came back with nothing detected as well as got moved on to microgynon contraceptive pill and now i am suffering with seriously bad stomach cramps where i have to bend over to walk and i am bleeding alot more heavier and it is as much as a period flow and is red blood now do you have any idea what this could be ??

please help me