Hi, Welcome to Health care magic forum.
Metho trexate usually does not show the effect on the weight,that is loss of weight.
It may be due to some other reason, like
lack of appetite, absorption, intake of diet, etc.
I advise you to consult a physician for diagnosis and treatment.
Take more of calories, fats, fries, oily foods, icecreams, and
protein supplements.
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.