Implantation bleeding?

Hi! I'm just wondering....if I may have experienced implantation bleeding. On the 21st- cycle day 27 for me, I thought I started my period - it was a little more brown than it usually is but it only lasted a few hours and has since ceased. No cramps and no more bleeding. I have anywhere from cycles lasting 28-40 days so if nothing happens I will test on the 3rd of July...anyone else experience implantation like this ??