Hello Good Evening, Headache can be a side effect of mobile phone and long duration talk in the night, less chances due to sexual urge. As your GF has issue of missed period frequently, which is due to some common reason like: -Pregnancy -Menopause -Stress and anxiety -Excessive weight loss, or weight gain -Hormonal imbalance -Hypothyroidism -PCOS Menopause and pregnancy are not applicable in this case but any of rest of the others can be a cause for her missing period, so please go through proper evaluation to get other causes like hypothyroidism or PCOS. PCOS (Polycystic ovary syndrome) produces symptoms in approximately 5% to 10% of women of reproductive age (12–45 years old). It is thought to be one of the leading causes of female sub-fertility and the most frequent endocrine problem in women of reproductive age. The principal features are anovulation, resulting in irregular menstruation, amenorrhoea, ovulation-related infertility, and polycystic ovaries; excessive amounts or effects of androgenic (masculinizing) hormones, resulting in acne and hirsutism; and insulin resistance, often associated with obesity, Type 2 diabetes, and high cholesterol levels. The symptoms and severity of the syndrome vary greatly among affected women and her abdominal pain can be due to irregular menstruation. So go for a USG, TSH and other investigation to find out cause of her frequent amenorrhoea. Regards, Dr. Naresh Jain.