TTC Newbie to the Extreme

I finished my last BCP pill pack at the end of September and we've "officially" started TTC as of October. I know technically as soon as you go off the pill, there's a chance that you can conceive, but I know the lining of the uterus is generally thinner when you're on the pill. About how long can it take for the hormones to completely leave your body and the lining to return to normal?