Missed a day (?) very confused. Please help.

I'm on the mini pill and I thought I've been very good about taking my pill everyday at the same time. But yesterday, when I looked at my pack I still had the pill for Monday & it was Tuesday so I was confused but I kind of shrugged it off. Now it's really bothering me, so much it has kept me awake and worried. I don't remember missing a day. I haven't had sex in the last few days but it worries anyways. I've never really been on the pill before and I hear that after having a baby you are more fertile. So before I do get "down and dirty" I NEED to know if this is something I should be worried about? Is it an easy fix?