Im way too skinny, how can i be fat?

"Fat" is not usually: Healthy. Would see your physician ; possibly a nutritionist to work toward a healthy weight in a healthy manner.

Weight gain: Without knowing your age, height, weight, ,metabolism, diet, life style, doing a full examination, reviewing medications/OTC's, evaluating medical history, and then evaluating appropriate lab tests, your question can't be answered. Please do this right, see your Physician. Physician may, among other things, recommend a Nutritionist.