Dear Jackilynn: I am assuming that you are not using some type of hormonal birth control (pill/patch/Nuva Ring/shot/Mirena IUD). If you are using one of these contraceptives then the most likely causes would be either annoying breakthrough bleeding from the hormones or an infection of the lining of the uterus (eg chlamydia).

For women not using hormonal birth control, the most common reason for a menstrual pattern like you have described is not having an ovulation 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.

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 built up lining can begin to shed under its own weight producing prolonged/erratic bleeding.

There can be many causes for not ovulating: low thyroid, pituitary problems, ovarian cysts, physical stressors (eg sudden increases in exercise, crash dieting), emotional stressors (problems with boyfriends/girlfriends, money), increased body weight, anorexia, rotating shifts at work, etc

Women with polyps of the lining of the uterus or fibroids in the muscular wall of the uterus can also have prolonged bleeding patterns. Yet this is usually a chronic thing; it doesn't suddenly appear.

If your bleeding pattern does not level out on its own over the next month you should see a GYN or even your local family planning clinic. They can give you the most "for sure" answer.

Yours,
Jane