Im worried! Dark blood?

Ruth

Ladies I need help. I dont know if Im overreacting but I just started my period today, it was a week late. Yesterday afternoon I had a lot of pink discharge when I wiped. This morning I wake up with what I think is my period but (tmi) it wasn't red, its a dark red color, like dark red brown. It's not as heavy as my regular periods and the color is different. I dont know if that makes sense? Im also experiencing mild cramping, nausea, fatigue, a lot of lower back pain, dizziness and headaches. I took a pregnancy test yesterday morning thinking I might be pregnant but now that I have my "period" I don't think there's a possibility that I can be pregnant. If any of you have experienced anything like this please help! Thank you girls!