How long after taking Provera can you have unprotected sex?

I know my Dr told me to have protected sex 2 weeks before taking Provera to make sure I didn't get pregnant and obviously I wouldn't have unprotected sex while on Provera, but I am wondering how long after I take the last pill should I wait to have unprotected sex? Like how long does it stay in your system? I believe I read something like it stimulated your hormones something like 16-21 days after, but I'm am wondering if if that is from the first or last day you take the pills? I know this sounds like a dumb question, but I am married and we are trying to get pregnant, I am not taking Clomid with this cycle, we are seeing if the Provera would just do it... but I don't have another Dr appt until next month, I can always call and ask but I just wanted to see if anyone had this info before I did so. Thanks!