Is Irregular Menstruation Normal After Starting Birth Control Pills?

I just completed my first month using birth control (on a 28 pack, so I just finished the non-hormonal pills), and, from what I know, I theoretically should have gotten my period within a few days of starting the non-hormonal pills. I'm a few days into another, new pack, and I still haven't gotten my period. I've had protected (both on the pill and using condoms) sex in the last month. Is my late period just a typical irregularity considering I've just started the pill, or should I be worried?