Irregular periods after a year of birth control?!

Hi, I've been on Sprintec for close to a year now. I need some advice on whether this is normal or not! Middle of August, I had my period as normal, but it was incredibly heavy. Then in September my period came 3 days late and was very light - closer to heavy spotting. Now this past Friday I started the light period/heavy spotting 5 days before my period should come. I've been on birth control consistently for two years and on sprinted consistently for one. I've only had this happen when I was first starting BC and the times I've tried skipping a placebo week. Other than that, my period has been very consistent and predictable. Not sure what's going on. Help!!!