My periods used to be every 28 days, but now they come every 2 to 6 weeks. What is wrong?

There are several causes for abnormal uterine bleeding. Hormonal imbalance involving the thyroid gland, adrenal gland, pituitary gland, or ovaries may be the problem. The other common cause involves structural abnormalities of the uterus, cervix, or vagina. These include polyps, uterine fibroids, precancerous changes or even cancer. It is extremely important to be evaluated promptly when these problems occur. Many times, these evaluations can be entirely performed in the office. Sometimes, however, the evaluation requires surgery such as hysteroscopy, usually done as an outpatient.