Please check out this
sticky that explains it all.
Implantation bleeding is very rare and not scientifically proven. Just think, can something microscopic cause bleeding? The answer is no.
This may very well be your period early, we all get a strange period once in a while.
So, if you don't get your period next week, take a HPT using first morning urine, if that shows up negative, wait a week and test again.