YES U CAN! My sister did and she had been taking it for 7 years!
I got the depo shot many years ago. It is 99% effective. You should be fine. As the above poster said, any bc method has that small margin of error and can fail, but depo is pretty reliable. Expect to have very irregular cycles with depo though. I only got it (the shot) like twice and then didn't have a period for over a year. It took me a really long time to get my body regulated after getting that shot. So if you go a long time without a period, it doesn't necessarily mean you are pregnant. This shot will more than likely cause you very irregular periods so just expect that.
yes remember all birth control has that rare chance including depo. And from what I heard Depo is the most common to get pregnant on to be safe I would still use a back up method. Good luck and congrats on your baby