Long periods on birth control pill

Elisabeth

I started taking Noriday mini pills the ones with progestogen only, when i was on that one i had 2 period a month for then my nurse changed me to a new brand called Famylette/ Desogestryl i started taking it soon as my period started it is now the 16th day and im still on my period should i be worried? Why are those pills not working for me?