Birth control problems?

I was taking Yasmin (an oral contraceptive) and I told my doctor that I didn't want to deal with remembering to take a pill everyday. So we discussed other options. He gave me a prescription and when i filled it it was more pills. The first few months I was on the new pills I would get my period early... last month I got it early and than a week after I started taking the pills for the month I got my period again. Now this month I am 5 days late. I don't think I'm pregnant, but what else could cause me to be late while on this pill? The Yasmin I had it like clockwork.. I'm freaking out! Please anybody give me some answers!! Thank you.