Hello, I understand your feeling Thank you for helping us by sharing your height and weight. Coming to the head size if the size of head is not proportionate with your size of the body know that it's completely familial aspect and anything cannot be done for that. To gain weight have 2 bananas followed by a glass of milk twice daily and you'll start feeling the difference. Bit having only this will not gain your weight but you need increase the food intake that you usually take and it has to be done gradually. Regular mass gaining workouts are there to gain weight you can follow that. Thank you