Hi, A dark brown thicker appearance to the period blood usually means that there is less blood and so it has sat around and become darker, as opposed to the brisker, bright red bleeding that happens when there is more bleeding happening. It s likely that you may not actually be ovulating fi your periods have been irregular and only 5 days apart. Failure to ovulate can happen when there is stress (physical or psychological) in the weeks prior to expected time for ovulation which is, in a normal cycle, 2 weeks before the period. You might want to go in to see your doctor to discuss this. Your doctor may want to give you a progestin such as Provera for approximately a week, to simulate the progesterone that you may not be making because of not ovulating. When you finish the Provera, after a day or two you will have a more normal period. Your doctor may also want to measure your FSH and LH levels to make sure you are not going into menopause, but this may not be necessary at this time. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Ivan R. Rommstein, General Surgeon