Once pregnancy has been ruled out with a reliable test (which should detect a tubal pregnancy as well), the most common reason for a menstrual pattern like you have described is not having regular ovulations every month. In a normal cycle, estrogen is produced all month. Estrogen is responsible for building up the lining of your uterus so you have something to shed each month. The good news is that you have enough estrogen to make a lining that does shed.
In a normal cycle, progesterone production increases following ovulation and release of an egg.. Progesterone "stabilizes" the uterine lining in preparation for a possible implantation of a new pregnancy. If you are not pregnant that month the levels of estrogen and progesterone fall, triggering the release of the uterine lining—your period.
So, if you do not ovulate, the estrogen build up of the lining continues, but without the usual ovulation associated progesterone. Thus, the hormone levels don't decline, and the lining stays up inside the uterus—as a missed/late period. Alternatively the lining can begin to shed under its own weight producing prolonged/erratic bleeding.
Causes for not ovulating are multifold: thyroid problems, pituitary problems, ovarian cysts, physical stressors (eg sudden increases in exercise, crash dieting), emotional stressors (problems with spouse, finances), increased body weight, anorexia, rotating shifts at work, etc.
Another possibility MIGHT be that you are ovulating regularly but an inadequate amount of progesterone is produced. This can result in prolonged spotting during the 7-10 days before onset of your "real" period.
An, given that this has been going on for a year I would urge you to go back to your OB/GYN (or GYN endocrinologist/infertility specialist) for follow up. They can give you the most "for sure" answer.
In Support,
Jane
Featuring Experts
Helpful Tips
Helpful Resources
Expert Blog
Below the Belt: Women's Health - Jane Harrison-Hohner, RN, RNP
From HPV to irregular periods to PMS to fibroids, Jane Harrison-Hohner, RN, is here to share her knowledge and insight...Read More
Related News
Report Problems to the
Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
Other Women's Health Information
More Related Communities
The opinions expressed in WebMD User-generated content areas like communities, reviews, ratings, or blogs are solely those of the User, who may or may not have medical or scientific training. These opinions do not represent the opinions of WebMD. User-generated content areas are not reviewed by a WebMD physician or any member of the WebMD editorial staff for accuracy, balance, objectivity, or any other reason except for compliance with our Terms and Conditions. Some of these opinions may contain information about treatments or uses of drug products that have not been approved by the U.S. Food and Drug Administration. WebMD does not endorse any specific product, service, or treatment.
Do not consider WebMD User-generated content as medical advice. Never delay or disregard seeking professional medical advice from your doctor or other qualified healthcare provider because of something you have read on WebMD. You should always speak with your doctor before you start, stop, or change any prescribed part of your care plan or treatment. WebMD understands that reading individual, real-life experiences can be a helpful resource, but it is never a substitute for professional medical advice, diagnosis, or treatment from a qualified health care provider. If you think you may have a medical emergency, call your doctor or dial 911 immediately.
Health Solutions From Our Sponsors
©2005-2013 WebMD, LLC. All rights reserved.
WebMD does not provide medical advice, diagnosis or treatment. See additional information.