On birth control and period late

I've been on birth control for about three months now. When I started my third set of pills I wanted to change the time when I took them to the evening from mid day and started the set one day earlier (from Sunday to Saturday.) I was just getting a little nervous since it has been three days since starting the placebo pills. I had unprotected sex just before going on the placebos and my period before going on the pill was usually irregular. I'm not sure if that's at all important to the subject, but I thought I'd mention it.

So is there a chance that I'm pregnant?