198x, I used to be very skinny when I was younger, have you lost this weight, through ilness, diet etc or have you always been slim. Also what age are you. If you want to gain weight you need to give consideration how best to do this and what foods to eat, whilst you need to increase your calorie intake to do this, using the wrong foods will not necessarily benefit your overall health. I managed to put on a stone by eating healthy foods and by taking protein drinks (I drank complan with milk, half a pint three times a day after meals) as I found there was only a certain amount I could physically eat. Discuss this with your doctor and perhaps asked to be referred to a dietatician for professional advice.