13 DPO...early AF?

So yesterday I woke up to a small amount of brown blood when I wipes, which is odd, as I never spot and my period has never in my life been 4 days early, yesterday was CD 22....usually a 27-28 day cycle. It was only spotting randomly throughout the day so I thought maybe implantation bleeding. Today it’s a very light flow but still very dark/ brown. Used a light tampon for 6 hours and it was maybe half covered. I took a test this AM, and thought I could see a faint line. What do y’all think? I’m also cramping, but I have a bicornuate uterus and endo so I cramp a lot. I should also add my periods are extremely heavy the first 2 days like soak through a super plus in an hour kinda heavy