Is It Normal To Have Light Periods When On Contraception?

I started taking crestor about 6 weeks ago. I'm taking 20mg a night. About 2 weeks after taking crestor, I was to get my period. I came a day late, left a day early and was even lighter than usual. The same thing happened this time. Not that I am complaining, I just want to make sure it's ok. I'm on birth control as well so my period is very regular.