Gwen, If you do a search for depo provera, you will find a few threads on it.

I only had one shot - was 1 month's injection instead of a 3 month one. I remember the paperwork that came with it said that it could take upto 18 months to get pregnant after using it.
When we saw a new GP recently for our FS referral, she said it was usually around the 9 month mark.

Nic