welcome to HCM
read your prob , your age is 23 n weight 20 kg, this is matter of worry, thats why you have that prob. first you rule out cause of underweight
by getting some blood test
,LFT ,Mountex test,
along with it you should take protine rich, fat riched, calcium riched diet. take more amount of fat like butter, ghee, etc if possible start bench pressing with light weight. after this trial you see change within month.
Dr aseem 9982583020