Yes you can increase,i am sorry that never mentioned your present weight and hight, age etc.. which is necessary for treatment
some underline diseases can also obstruct weight gain. so you must ruleout the diseases if any.
Do consult a physician or a homeopathic
doctor for help in diagnosis.
To increase the weight you must increase the intake of carbohydrates( rice etc), eat daily eggs and banana
Homeopathic tonic like Alfalfa
or Alfavena malt daily 4 teaspoon 1/2 hour before food for three months will definitly help to gain weight soon.