Well when you stop the pill it tells your body to get a period prematurely (withdrawal bleeding). The chances are in your favor that you are NOT ovulating. Usually any fast drop in hormones tells your body that you are already past the point of ovulation, there is no fertilized egg in your womb, and thats why you start to shed your lining.
Nothing is 100% though unfortunately. The body can and will do some unexpected things. You may ovulate. Some women have been known to ovulate while on their menses.
Just be sure to test for pregnancy before starting any new forms of contraception.
it is likely you do not ovulate during a withdrawal bleed BUT you can ovulate very shortly afterwards. It is common to have an early ovulation the first month off your pill. Be careful if you don't want to get pregnant!!