What Causes Delayed Periods?

Hi,



I'm 29 years old, married. I've a very good health. Some times I work out a lot on the treadmill. I've my periods every 27 days. I've never had a irregular periods till now as far as i remember. This time, I had my last period around 26th May and not having it so far scares me. I'm sure I'm not pregnant as my husband is onsite since an year. Please let me know if I should visit a doctor .....



Thanks,

Madhavi