It's hard to say if it's implantation bleeding or not.
I had implantation bleeding with this pregnancy. I had been on the pill for 10 years before stopping last year. I had a definite period a few weeks after stopping. About 3 weeks after this bleed, I had another. This was different from my period as it was a light brownish bleed. It only lasted a couple of days. On the 2nd day (so while I still had the bleed) I did a pregnancy test which was positive. It was also consistent with when I estimated I'd ovulated. Because of these reasons I knew it was implantation bleeding.
It sounds similair to what I experienced, but I guess it depends on how long your cycle is now. Or possibly your cycle is out of whack from the pill & it's another period.
You certainly could get a positive on an early pregnancy test now if you are pregnant, why not just do a test?