depo shot lasts for 3 months. in which time you cannot get pregnant. my doctor told it me it can take an additional 10-15 months for it to be completely out of your system. with that said, you still CAN get pregnant during this time, its just less likely.
Scroll down to 4.4 Special warnings and precautions for use - return to fertility
If you stop getting Depo-Provera injections, your period usually returns within 3 to 10 months but sometimes it may take 12-18 mths. Ovulation may return earlier and hence you can try for pregnancy when ovulation returns.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
My last shot was October of 2011... Still haven't gotten a real period now I think I might be pregnant. But I can't tell due to the fact my last "period" was 8 months of spotting!! Best thing is to just go talk to your doctor. There are all sorts.of tests they can do. Good luck.