How to gain a few pounds?

Anonymous
I don't know much about nutrition and health...I'm underweight by like 3 or 4 pounds and I'm wondering how I can gain weight. I've always been very skinny and the type that can eat whatever I want and eat any amount, and not gain a single pound. Two months ago I went to my doctor for an annual checkup and she mentioned how I had lost a few pounds from the previous year (completely unintentional). and so I was thinking "hey, I should probably gain a few pounds". Well, in the past two months I've actually lost two pounds instead...i don't know how that happened. Its not like I exercise and I'm burning fat. I sit on the couch and snack all the time haha. I'm not at an unhealthy weight but I'd like to be closer to the average weight for my height.

Currently, I'm 5'9" and I weigh 118 lbs.
How to gain a few pounds?
2 Opinion