How can I gain some weight in a healthy way?

I was just 98 pounds not to long ago...but I just lost 3 pounds and not sure how. any advice on how to gain weight but in a healthy way?

Eat regularly, and healthy...

Omega 3 fatty acids sources like tuna, salmon, flax, and walnuts, poultry, nuts, seed, legumes, chickpeas, kidney beans, peanut butter, omeletts, whole grain cereals, rice, pasta, granola, bagels, cornbread are a good source. With veggies, try avocados, olives, potatoes, peas, corn, squash, Fruits like canned fruit in syrup, dried fruit and fruit nectars. Use protein products and nutritional supplements like Ensure or Instant breakfast drinks. Use milk instead of water in cereals, soups, sauces, mix cooked chop meat, wheat germ, nuts, beans, or cheese in casseroles, pasta and side dishes. Try and add 300-350 calories a day to your normal intake. Eat larger portions and you will gain some weight.