Thanks for your query .
SLight bleeding / spotting off and on is the most common and annoying side effect of the Depo shot, as you have rightly observed.
As you have already taken the shot, do not use any other method right now.
You are bound to it until February.
Do use a backup method like condoms during the first month of the Depo shot, as the hormones stabilize and it starts to work.
Also, yes, return to fertility
and normal cycles does take a while longer on the Depo.
It would be wise to switch to another method if this bothers too.