Only got one depo-provera shot ever haven't got my second one in 3 months been sexual active and i'm getting blood spots here what does that mean ?

Unpredictable: The bleeding patterns with depoprovera are unpredictable. You are right that for some in takes the period away. For others it causes irregular bleeding. There is no "normal" for Depo-Provera users. The longer you are on it the higher the chance of no periods. The Mirena (levonorgestrel) iud may be a better option for you if you want to avoid pregnancy and stop having periods.

Depo out of system: The DepoProvera is getting out of your system. It takes a while for ovulation to return after Depo wears off and irregular spotting and bleeding are normal until ovulation returns. You can still get pregnant at any point so, unless you want to be pregnant, you do need to be using something for contraception. Hope this helps.