Hi, Leelee . . .
Most dysfunctional uterine bleeding (90%) is due to estrogen breakthrough bleeding, a result of anovulation. Since ovulation has not occurred, progesterone is not available in sufficient quantities to stabalize the endometrial structure. Due to this lack of progesterone, the lining continues to grow under estrogen influence, but it is not mature and is very fragile. A small decrease in estrogen level results in bleeding, usually heavy. As one site heals, new sites break down in an asynchronous manner. The amount of bleeding depends upon the height of the endometrium and in the drop in estrogen. There is no rhythmic vasoconstriction or orderly colapse present to induce stasis and clotting. Signs of anovulation are sudden onset of excessive bleeding, too frequent flow, too heavy flow, too prolonged flow, occasional clots, lack of premenstrual symptoms, and, of course, absence of pelvic abnormalities.
Identified causes of anovulatory dysfunctional bleeding are: CNS dysfunction (ie, stress, chronic fatigue, obesity [due to more free testosterone], malnutrition, perimenopausal), ovarian dysfunction (ie post tubal ligation), follicular phase defect (ie, immature folicle formation or persistent unruptured follicles), luteal phase defect (ie, premature corpus luteum degeneration or persistent corpus luteum), temporary estrogen withdrawal at ovulation, endocrinopathies (ie, thyroid, diabetes, adrenal) and high prostaglandins.
OK, so this is more than you probably cared about knowing. Take what's useful and dump the rest.
I also would be very concerned about your being on OCs and smoking, although it is a common treatment for dysfunctional bleeding, but usually only short term (3 months or so).
I hope you find answers at your doc's appt.