Wondering where your period is? Why it is late? Either you know you cannot be pregnant because you have not had sex, or the pregnancy tests you are taking all come up negative. So what is the issue? The answer may not be as clear as you want it to be. There are quite a few reasons this could be happening.

15 Possible Reasons Your Period is Late (But You are NOT Pregnant)

Stress

Stress can affect many things in our lives, including our periods. Sometimes you're so stressed out that your body decreases the amount of hormone needed to ovulate. Emotional and physical stress can both be to blame. Things in your work or personal life may cause sudden spikes in your stress levels, or you could suffer from chronic stress. Either way, if the timing of the stress delays your ovulation, it will delay the start of your period. Working on reducing your stress, and taking the time to relax, will help your cycle get back on track.

Breastfeeding

If you are breastfeeding, it is common for cycles to be irregular for the first few months after they return. Research shows that breastfeeding may significantly delay the return of fertility. Personally, my cycle does not return for over a year postpartum due to breastfeeding. By nursing your baby on demand, you create a natural sibling spacing. While breastfeeding, you may experience irregular periods or spotting as a result of variances in the hormones released while breastfeeding. This could be a result of a decrease in nursing because of a sickness in your baby, teething, getting a sitter, or just changes in appetite. This is why some women may have a first period after delivery, and maybe even begin having a normal period while breastfeeding, and then stop as an increase in nursing can cause menstruation to stop. Your own hormonal balance prior to breastfeeding may also affect how your cycle functions while nursing.

Recently Off Birth Control

Because hormonal birth control takes over the hormones of the body, when it is withdrawn from the body, there will be a period of time before the body gets back on a consistent cycle. This can mean irregular cycles with frequent bleeding, lighter periods, heavier periods, or delayed ovulation and periods. The body should adjust within 6 months of discontinuing hormonal birth control.

Sudden Weight Loss

When your BMI is below 18%, the body often stops menstruation. A low BMI may result from excess physical training, lack of calorie intake or genetics. If you get your BMI back to normal levels, you may start experiencing a normal cycle again.

Extreme Exercise

Excess exercise can impact your reproductive hormones. By causing inadequate estrogen production, your cycle may be extremely delayed or missed all together.

Weight Gain

Sudden weight gain can also affect ovulation, since too much body fat can lead to increased production of estrogen.

Illness

Viruses, colds, and flu all effect the body just as stress does. If the timing of your illness is prior to the body ovulating, ovulation may be delayed which also delays the start of your period.

Change in Schedules

Changing schedules can really throw off your body clock. This is particularly true if you go from days to nights at work or vice versa.

Change in Medications (Or medications in general)

Medications can cause delayed or shortened periods, menorrhagia (heavy or prolonged bleeding or amenorrhea (no menstruation). For example: antidepressants and high blood pressure medicine. Don't overlook antibiotics or other commonly prescribed medicines.

Pituitary or Thyroid Issues

The thyroid gland is basically your body’s internal thermometer, regulating functions such as internal temperature and metabolism. Hormone levels produced by the thyroid that are too high or low can cause late, missed, or irregular periods, and even menstrual spotting between cycles or menorrhagia.

Poly Cystic Ovarian Syndrome

Over 20% or women are assumed to be suffering from PCOS. It occurs when a woman does not ovulate, which causes a disruption in the normal relationship between the hormones, brain and ovaries. PCOS is when the follicle moves to the outside of the ovary, but does not release it. Instead, the follicle becomes a cyst, and the normal progesterone surge does not occur. The lack of progesterone is detected by the hypothalamus, which continues to try to stimulate the ovary by increasing its hormone production (Source)

Endometriosis

Endometriosis is the buildup of uterine lining tissue outside the uterus, most often in or on the fallopian tubes, ovaries and pelvic area. It is thought to be caused by or exacerbated by too much estrogen in relation to progesterone, and it can cause organ dysfunction or intestinal blockage. Symptoms include painful menstruation and frequent and severe bleeding with an irregular cycle.

Autoimmune Disease (Celiac, Lyme, etc)

Chronic illness can wreak havoc on the body, as many autoimmune diseases mimic other illnesses by disrupting different systems of the body. They have the ability to alter everything from the woman’s menstrual cycle to brain development.

Birth Control

A low-dose pill or the hormonal IUD may cause your period to slowly disappear. These hormones are foreign to the body and can cause damage to more than just your cycle. Taking a pill off-schedule or adding a medication to your routine can alter your cycle.

Peri-Menopause

This is the period of time where you are transitioning from reproductive age to a non-reproductive age. Your periods may be lighter, heavier, more frequent or less frequent - but mostly just not normal. It can happen earlier than you expect.