I've Had Implanon For About 2 Years Now And I've

I've had implanon for about 2 years now and I've spotted only a couple of times if that while on it. Recently on new years day I got my period it was a lot heavier, like a regular period. I only had it for a few days at the most. Then yesterday I got it again, heavy and bright red. I'm having a lot of stomach pains and midol isn't helping. What could this mean? Am I overreacting or could I be pregnant?