Well, i'd say maybe the dosage is not quite accurate for your body, maybe you need to try a different kind or different dosage. Of course it could be something else too, some people have different sensitivities to drugs (and there has been a study lately suggesting that body weight can the accuracy of the pill, I don't have the source right now, but knowing how other drugs work, that seems reasonable). Talk to your doctor about it if it stays a problem. Certainly there is a possibility that it could affect the effectiveness of the pill you're taking. (not saying that is will, but it may, and that's reason enough to check it out i'd say).

Good luck