i had mine on for two yrs n a half.. took it of in late may got my first weird period (on and of for two weeks) in june june .... n found out i was pregg in july in a er visit on a possible miscariage so it all depends on your body and your hormones ...
It can take up to a year for ulyour body to regulate after coming off of birth control. Being that you just came off of implanting, I'd say its your body trying to adapt to not having it. It's really hard to say since you can have cramping and not ovulate or be pregnant.