brown spotting instead of af?

Like the title says, I've had brown spotting on and off for four days. I tested three days before af and got a bfn. The spotting started two days before my expected period and has lasted so far for four days on and off. Not enough for a pad or tampon. It'll be there when I wipe and the next time I go to the bathroom it's gone. I've worn a tampon each day to work expecting af to come but when I get home and take the tampon out, there's just brown on the tip of the tampon and the rest is completely white. My question is, should I count this as a period? Should I even bother testing again?