I am actually going through the same, almost exact thing as you are. I however, am not on the pill. After my last menstrual cycle another (but unusual one due to consistency and color and only lasted for two days) started eight days later, which has never occurred. My cycle, like yours runs like clock work also. Tomorrow I am going to give my doctors office a call and speak with the nurse just to be sure it is not an issue that my doc will need to see me for. Try not to worry too much. I would also advise that you to call your doctors office too. Hey, what could it hurt? I'd rather know for sure than to wonder myself!
Let us know how everything goes!