I've been on the depo-provera shot for 3 years i've never a period my next shot is march 25. i got my period today. is my shot still working?

Breakthrough bleed: Your magical Depo-Provera shot was designed to suppress ovulation and the build up of a uterine lining so it's no surprise that you weren't having periods, however over time you can accumulate little bits of lining/endometrial tissue that reaches a critical mass where it then sheds. This can be normal add long as you're on time with all your injections.