Brown blood

I've been off the pill for a year now, and I've had brown discharge for the first time in a few days. Not pink/red, but really brown and very little. Could this be implantation? I've already tested, but it was negative. I also heard that you can only test after a few days. My cycle is irregular, and to let it go, I haven't used ovulation tests, so I have no idea when my period is due.

Are there others who have experienced this?