It's a known side effect of depo to have a delayed return of fertility for up to 18 months.
I suggest charting. Get the book Taking Charge of Your Fertility by Toni Weschler, it will teach you how (you can even find it at the library, so it's free!). Figure out if you are ovulating or not. If you are not ovulating, take a B complex vitamin (contraceptives increase your need for B vitamins, which play a significant role in regulating fertility) and vitex (chasteberry). These are easily available at healthfood stores.
at 9:13 AM on May. 19, 2011