Implantation bleeding or early AF?

I have tested on the 25th and the 27th about 8-10dpo and they were both negative. I woke up to a brown blood yesterday morning around 5:30am while getting ready for work. I suited up as a precaution for the day. Around 12:30 I cleaned up on my lunch, a little brown but I have not bled since yesterday after lunch. AF is due tomorrow. Is this signs of AF being 2 days early or not coming at all and signs of implantation? I don't want to waste a test if AF is right around the corner, how long should I wait to test if it's late?