A period can be late for many reasons beyond pregnancy. Common causes include stress, significant weight changes, intense exercise, hormonal imbalances, medical conditions like polycystic ovary syndrome (PCOS) or thyroid issues, medication effects (such as birth control or antidepressants), breastfeeding, and the onset of menopause. Stress can disrupt hormones and delay periods, while conditions like PCOS cause irregular ovulation. Thyroid problems may also lead to missed periods, and various medications can interfere with menstrual cycles. If periods are irregular for several months or accompanied by other symptoms, consulting a healthcare provider is recommended to identify underlying causes and get appropriate treatment.