Iv'e Been On The Pill Now For A Couple Of

iv'e been on the pill now for a couple of years and iv'e recently started bleeding and having really bad period pain. i most definitely should not be getting my period. This happened last year, i went and saw my doctor and she put me on a different pill that was supposed to be stronger but its happening again. i originally went on the pill to help with making my period regular and to reduce period pain as it got to a point of being unbearable. not sure if its just this particular pill that isnt working for me or if i should go see someone who can run tests, my doctor just doesn't seem to know what shes talking about!