Do I Have Low Test at 19 Years Old?

Let me get a jump on what @KSman will ask for.
Please read the stickies found here: About the T Replacement Category - #2 by KSman

advice for new guys - need more info about you
things that damage your hormones
Need to test E2

Read the stickies and you will know more than most doctors.

Brittle nails can also be from thyroid issues?
Using iodized salt to support thyroid hormone production?
Feeling cold easier that before?
Outer eyebrows sparse?
Please check oral body temperatures as per the thyroid basics sticky. That is a good overall measure of thyroid function.

Your TSH looks to be a big read flag to me.