Implantation?

Emily • Our rainbow 🌈 baby has arrived! April 3, 2017.
I've had very very light brown spotting yesterday and today (need to wipe to see it). I'm due for AF tomorrow but have never spotted prior before. 
Could this be implantation? I've read that it usually comes around 12dpo; yesterday would have been 13dpo. 
When should I test? I tested yesterday morning and got a negative on the cheap internet dip-ins.