late period

I was supposed to get my period 6 days ago. 5 days ago I started the pill for the first time. It's not uncommon for my period to be 4-5 days late, and the doctor did a pregnancy test when she perscribed the pill (so I'm not pregnant). Could the pill postpone my period? I've been feeling a lot of pms symptoms (more than normal) and am wondering if it's the pill's hormones or the late period.