i'm about 98% sure I'm not pregnant.. BUT... (just thinking out loud here)

so my period was late. I took a pregnancy test the day after it was due and it was negative. then my period started at 4 days late.. but with the most awful pms(maybe?) symptoms I've ever had. intense stomach pain and nausea.. back pain so bad I could hardly move. THEN.. (and I've always believed kids and animals can sense things we can't) my little niece TOLD me I'm pregnant. didnt ask. told me. trying not to get my hopes up but that was freaky. so I looked up period but still pregnant and it happens! possibly implantation bleeding? but idk because it wasn't light.. not heavy either, but not light enough, I thought. then it ended! after just 2 days.. it's usually 4 or more. SO IDK MAYBE I'M PREGNANT.