I would think your chances of getting pregnant at 47 are pretty slim to begin with.
I am 43 and an pregnant with my first child naturally...no help from Dr.s. I too had been on nor plant and other birth control for years. Last 5 years I used ovulation chart to avoid pregnancy...easy to do in a long term monogamous relationship....and this past year used the chart to assist with concieving.
You 47 but until you go through menopause, it is responsible for you to use the ovulation chart in conjunction with condoms or spermacide cream to prevent pregnancy, once you are off the Depo.
Thanks for being so responsible about reproduction! Funny how many women are on this site who lack willingness to use birth control but then complain about being single mom's or pregnant again by a spouse they do not want to be with