Periods last not long enough to show there is enough lining to be used as a ‘baby nest’.
Not enough extra resources to make a baby with – the sole purpose of periods.
Either you are super stressed (thus creating inner heat driving out the blood too soon) and not able to eat well, and/ or there are little nutrients spare to make the a great qualty egg to be lost.
May have an iron deficiency as a result of over bleeding – but the low thyroid function usually due to presence of heavy metals and not enough iodine will start this off.
Need more water, rest and exercise, less chemicals and stressors.
Acupuncture and Chinese herbs are great to replenish – after looking to the basics as above.