What are the effects of expired birth control pills?

So I'm out of birth control pills. I kept a pack set back incase I ever ran out before I could get in to see my doctor and get a new perscription. I've had the pack set back for about a year or two and I can't get in to see my doctor till the middle of November. I'm a few days into the pack and I've started worrying of it could cause infertility or just not be effective at all.