Periods

I started the pill about 2 months ago and the period i've got I was extremely light for about 4 days then I had a normal period for another 4 days then it started going very light for about 3 days and now it's a heavier flow again, I usually only have periods for about 4 days. I was just wondering is normal for my flow to be light then heavy then light and then heavy and if it's normal for the pill to make periods last longer