Normal menstrual cycle

Cycle length
3-5 weeks (average of 4 weeks) from the first day of one episode of regular menstrual bleeding to the first day of bleeding in the subsequent cycle

Duration of menstrual flow
3-7 days (average 4)

Amount of menstrual flow
35ml; more than 80ml is abnormal

Quality of flow
Nonclotting blood and endometrial debris
Cycles at extremes of reproductive age tend to be anovulatory and often are prolonged, though they may be shortened in some individuals

So if that is considered a normal menstrual cycle, you may be wondering what is happening to you and to your cycle. It is very stressful when normal bleeding, as we know it, turns abnormal. I completely can relate. It is not easy to go through at all! The biggest concern is, "What is wrong with me?" So let's get to the definition of abnormal uterine bleeding and dysfunctional uterine bleeding and some of the reasons it occurs.

Abnormal Uterine Bleeding (AUB) refers to bleeding caused by an underlying disease or condition of the reproductive tract.
Such as:

Ovarian cysts
Uterine fibroids or polyps
Endometriosis
Endometrial cancer
Cervical polyps or erosion
Cervical cancer
Vaginal lesions
Blood coagulation disorders
Pregnancy or postpartum related bleeding
Hormonal disorders such as thyroid disease, problems related to an intrauterine device (IUD), anorexia, dramatic weight loss, or vigorous exercise.

Dysfunctional Uterine Bleeding (or DUB) refers to alterations in uterine bleeding occurring during your reproductive life as a result of anovulatory cycles (failure to ovulate). If you don't ovulate, your ovaries do not produce progesterone, so the lining doesn't shed the way it normally would. Instead, in continues to grow and then starts falling apart, resulting in irregular spotting, heavy bleeding, or bleeding throughout the month. Some women will experience fluctuations in estrogen levels that result in erratic bleeding with increased frequency. These normal responses to fluctuating hormone levels can be very disconcerting. This can be treated with medications, usually progesterone. Pills with progesterone in them can make the lining of the uterus become spongy, as it would if you ovulated regularly. Over two or three cycles, the lining returns to its normal thickness. Then, when ovulation resumes, the drop in progesterone each month causes normal menstrual bleeding.