Hi, Welcome to Health care magic forum.
As you describe, you are low weight,for your height, and this may be due to some factors like non absorption,limited intake,
anemia, or some disease.
Lifting weights may not have any relation with the height of the body.
You can try to gain weight medically, so i advise you to consult a physician for diagnosis and treatment.
I usually prescribe to my patient with such requirement injection of anabolic
steroids periodically,
protein supplements, multivitamins, and enzymes.
Take more of green leafy vegetables, pulses, sprouts, and protein rich foods,to have good health.
Wishing for a quick and complete recovery. Thank you.