Help! I need a healthy eating routine?

Usually I only have big bowl of cereal with milk every morning, then i just have some juice for lunch, go out to eat with my friends at night (. I have school and work at the same time. I'm a pharmacy technician so it's stressful. I drink water most of the time when i feel hungry, because i'm too tired to eat. I'm 5'3 and weigh 107 lbs, but now only 104. and when I'm busy i just have one meal a day, and i get acid reflux. I usually have it, so I take medicine almost everyday. I have a high metabolism and I can't gain weight easily. It doesn't affect my skin, i have fair skin, but I keep losing weight!! Btw, I'm only 19, so i need a healthy eating routine please, I want to gain few more lbs. Thanks, i really appreciate it