My period's late this month, when should I mention it?

I had a baby 6 months ago. I've had my period, and though it's been irregular, it always comes. This month however, it hasn't come yet. I know 100% that I am not pregnant. When should I see a gyno or Dr. about it? How long should I wait? When should I mention it to someone?

Mention it if you miss a month or two months. Its like work, we work at the same place, but get to the workplace at different times. Even though we work at the same place and even wake up at the same time, most of the time.