A shift of about a week in your cycle for two months in a row can happen with stress, diet, sleep, or weight changes, and it doesn't always mean something is wrong.
Next Steps
If it continues for another cycle or two, or your periods stop altogether, please get a hormone panel and pelvic ultrasound done with a gynaecologist.
Health Tips
Please don't start any
vitamin or supplement on your own for this. A doctor needs to check what's actually causing the delay first.