I don't have personal experience with the depo injection, but I wanted to offer some reassurance. I know that a lot of women have trouble when coming off of any of the types of birth control. Some can luckily adjust quickly, but it takes a while longer for some women.
However, it will happen. Here are a couple of BFP stories I found for you to look at. I know you can find more if you search "BFP after depo injection" on google. I hope your cycle regulates soon. Good luck!
story 1
story 2
As far as the temps, are you using a site to track them?