Thank you for your query Would you please clarify a few things for me? 1)are your periods regular? 2)do u have any thyroid hormone imbalances that you are aware of? 3)are you on any medications? 4)have you gained or lost more than 5 kg in the past month? The menstrual cycle is controlled and regulated by hormones. A regular cycle consists of a follicular phase(from the start of your period till you ovulate), ovulation phase (egg is released by the dominant follicle) and the luteal phase (the phase in which you can get pregnant - the uterus is primed for a possible implantation) The length of the luteal phase remains pretty much constant for a particular woman, although there are variations between women(if it s 12 days for you, it will be remain constant almost always. The normal range is from 10-14 days) The follicular phase, however, can vary. Usually regular, it may be influenced by extraneous factors like travel, major life changes (getting married, migrating to a different city, for instance) and can delay the ovulation, which in turn can lead to a delayed period. I think this is the case for you. Occasionally functional ovarian cysts occur during the child bearing age, which interferes with the hormonal regulation and may delay period. These usually go away within a couple of months and do not require treatment. If, however, they become too if or become painful or don t go away, it may need to be removed. I recommend you wait till your period is 15 days late, take another HPT, then visit your OBGYN, who could examine you. You may have an ultrasound of the pelvis to rule out cysts and check for pregnancy or anything else that could be delaying your period. If you have a simple cyst, you may have the option of waiting it out with regular monitoring or taking medications to suppress it. Discuss with your doctor about your options and take an informed decision. Rarely a cmplex cyst may occur which may need to be removed. Thyroid imbalance can cause irregular period. If you take medication, let your doctor know. Hope this helps, Please feel free to get back to us if you need further clarification Wish you good health