how fustrating!! it may just be your body needs to adjust to it, when i started the pill, i was told it may take up to 3months for my body to get used to it before you settle into a regualr cycle.
mind you, i had the exact same problem when i was on the injection, so i can understand how annoying it must be for you. thas why i changed to the pill, and i've ben fine since.
go have a word with your doctor, it may be that you need to try a different type of pill as your body could not be agreing with it for some reason..
hope this if of some help, good luck xx