Could brown spotting mean something beyond AF?

My period is three days late, which has never happened. Last night I got a little bit of brown spotting. When I woke up this morning, my panty liner was completely untouched. This morning I've had a little bit more brown discharge, but not a lot. Mostly when I wipe. I had brown discharge 10 DPO. Which I thought might be implantation bleeding. But my boobs are huge right now, last night I felt very nauseous and flu like. This morning I thought I was going to throw up. I've had crazy mood swings, very emotional, and a lot of head aches. Should I even test?