Depo Provera stays in your system from 120-200 days. If you're having period problems and are having breakthrough bleeding while on the pill since October, it's likely something to do with the brand of pills you're on. Pills come in many different combinations of hormones and strengths for different types of woman with different types of bodies and needs.
If you continue to have problems, you should see a doctor to find out exactly what is going on. It's likely they'll just try you on a different brand of pills. Sometimes it takes a couple switches before you end up with a combination that will work well for you.
Good luck to you.