Implantation maybe??

Sorry TMI but- starting yesterday I had brown discharge, thinking it was the start of AF I put a pad on before bed. Woke up, nothing was there but put a pantyliner on just in case. All day today all there’s been is dark, dark almost brown spotting but not enough to fill the pantyliner. When I pee there’s no blood in the toilet or anything like you would with a AF. I’ve been super fatigued and nauseous all day. I don’t track much, just my period on Glow cause we aren’t totally TTC but not preventing it either, just being carefree to not put stress on ourselves. If this is IB, when can I test? I don’t want to test too early but I’m getting anxious!