Does Taking Phentremine Capsules Affect Periods While On Birth Control?

im taking these pills i got offline called phentremine but they look nothing like the real ones. i think they might be just a herbal supplement, their in a clear capsule and have a light brown powder in them. im on birth control also and its not time for my menstral cycle to start yet but it kind of has, its kind of bloody and clear slime. my question is, will taking those pills mess up my menstral cycle even though i take birth control?