I'm 114lbs 5'7, i can't gain weight no matter what i eat, my doctor says there's nothing wrong with me health wise. what can i do to gain weight! ?

Eat healthy high: calorie foods. Eat 6 meals/day. Work on strength training to build large muscle groups. Workout w heavier weights w fewer repetitions. Sleep at least 8 to 9 hrs/night. Hydrate well w water. Foods to help w healthy weight gain: almonds, cashews, pecans, sunflower seeds, flax seeds, walnuts, hummus, Avocados, granola, trail mix, dried fruits, extra virgin olive oil, canola oil & protein shakes.