Based on what you described, your body may not be developing normally for your age. Even though you started puberty at 13, it sounds like your growth and physical changes may have slowed or stopped, and being very underweight with hair loss is a sign that something inside the body may be out of balance.
This is not your fault, and it does not mean something is permanently wrong, but it does need to be checked.
What this could mean
Your body may not be getting or using:
Enough hormones that control growth and puberty
Enough nutrients (like iron, vitamins, or protein), even if you eat a lot
Or your body may be under stress and has slowed development to protect itself
Because of this, you may look younger than your age and have hair loss and low weight.
What you should do next
The next step is medical evaluation, starting with blood tests. These tests help doctors understand what is happening inside your body.
The blood tests usually check:
Growth and puberty hormones
Thyroid (which controls metabolism and weight)
Iron and
vitamin levels (important for hair and energy)
General health and nutrition
A doctor may also:
Measure your height and weight carefully
Check your stage of physical development
Order an X‑ray of your hand to see if your bones are still growing
Why this is important
If this is checked now:
Many causes are treatable
You may still be able to continue developing normally
Hair loss and low weight often improve once the cause is treated. Many young women with similar symptoms do very well once the problem is identified. Getting blood tests and a proper evaluation is the most important next step.