What Causes Light Period While Using Birth Control Pills?

I am 26 years old. August 1st I started taking birth control to switch the time of my period since my wedding is coming up. My doctor said to take two months in a row and to skip a period so it would come earlier in the month. Up until I started taking it, I did not have any trouble with my period. It came at the same time every month for 7 days. When I started taking it everything was fine. At the end of the month when you take the placebo pills, I started another pack. Two days into the new pack I started getting light brown smudging. Since then it just seems like a very light period (some red some brown) ever since. It will be two weeks tomorrow, that this has been going. Is it normal? Is my body just getting used to birth control?