Pill Period???

Kirstie
is this normal? 
I recently started the pill, on the forst day of my last period (25th) and i had my normal period that lasted slightly longer at 7 days rather than 5. Nothing reallyunusual, but then a week after coming off my period I came on again (on the 9th) and I'm still on now. It keeps chamgin from a heavy flow to hardly anything, then back to heavy again and sometimes it stops altogether for a few hours.
Is this just aide effects of the pill, or possibly somwthing else that I may have to be concerned about?