Skip to content
My WebMD Sign In, Sign Up

continued...

It's another side effect of the hormone called prostaglandin. It causes the muscles in your bowels to contract. This is why you can have loose stools, diarrhea, and stomach pain when you get your period.

7: What if My Cycle Has a Mind of Its Own?

It sure would be nice to know exactly when you'll get your period. But that depends on when your body releases an egg, called ovulating. If you don’t ovulate every month (and you may not at first), you won’t have regular cycles.

It's tricky for almost everyone to pinpoint a start date, except women taking birth control pills, which regulate your cycle.

Many women get their period about every 28 days. A regular cycle is from 25 to 35 days. To determine the days in your own monthly cycle, count from the first day you start bleeding until the first day you start bleeding again.

You may not get the same number of days next month. So it's a good idea to be ready for your period to start a bit sooner than you expect.

8: Why Did I Miss My Period?

If you're having sex, your first thought is apt to be, ''Yikes, am I pregnant?'' You could be. Another possibility is changing hormone levels.  

Check with your doctor when:

  • A pregnancy test is negative and your period is still missing.
  • Your periods were once regular, but no longer show up when they should.