new pill pack, potential pregnancy.

Is it safe to start a new pill pack if there's the potential of being pregnant? I was supposed to get my period this past Saturday. I had some minor bleeding for about 24 hours on Monday but that was it. My period is normally heavier and lasts about 5 days. I am supposed to start a new pill pack tomorrow but am not sure if it's a good idea. I didn't get to call my doctor to ask today and the office isn't open tomorrow.