Bleeding/not bleeding

A week before my period was due I had very very light spotting. Not even enough to need a pad. I thought this was the beginning of my period cause ive never experienced it. But after a day it stopped. So ive been expecting my usual period which also hasn't came. Im on day 36 of my cycle (im usually 28 days) ive just done a HPT and its negative. I don't understand? Have I tested too early?