Irregular periods that are now more than a week late can happen for several reasons, hormonal imbalance, stress, and significant weight change are the common ones at your age, and a condition like PCOS is also worth ruling out. Since this keeps recurring for you, it is worth looking into the underlying cause rather than treating this as just one off cycle.
Next Steps
If there is any chance you could be
pregnant, take a home urine
pregnancy test first. Otherwise, see a gynaecologist for a pelvic ultrasound and hormone blood tests, including
thyroid and PCOS markers.
Health Tips
Start noting your cycle dates from now on, it helps your doctor spot the pattern much faster at your visit.