My period has come late and only lasted for 1 day and do not understand why? im not pregnant or anything and they usually last 5 days or more.

Irregular periods: Irregular periods are one of the most common problems obgyns treat. If this is one time problem it usually resolves on its own. If this is a recurring problem you should be evaluated. Infections, polyps, fibroids and hormonal changes can cause. Remember cycles come every 21-35 days -- not necessarily monthly. Ovulation occurs once per cycle.