Weird bleeding

Hey :)

So I was supposed to have AF, bleeding started a day late.. I didn’t have any of my period symptoms other than mild cramping. Usually cramping is so bad it stops me in my tracks some days. My “period” was lighter than usual and only 4 days .. maybe 3.5 days.. so you guys think it was AF ? Or implantation.. I was reading that sometimes implantation can mimic a period and last for several days. I’ve been nauseous, and have been having so many headaches lately which is out of my norm. Should I take a test ? Also my LH level the day after the bleeding was visible, and keeping a steady 0.18 range..