Hi I'm Currently 10 Days Late On My Period, When

Hi I'm currently 10 days late on my period, when I was supposed to be on my period there would only be a slight bit of blood when I wiped only, barely any there and more brown looking than anything. For a whole day now I've had diarrhea like crazy my stomachs been hurting but I've taken two tests and they both came back negative. I'm so confused and my period last month was two days late and I only ended up being on it for two days but those days were extremely light.