Help with gaining weight- I’m not the type to eat.

Hey there everyone, I’m Alexandria.

I’m 5’0 and I weigh roughly 80 lbs/ 36 kg

I’ve always struggled with weight and doctors say I’m healthy but it is underweight, (they say as long as I don’t get sick I’m fine)

I’m struggling eating (I can eat like all my food and be fine but after one meal like that I’m done for the rest of the day)

Right now I’m working on carbs and trying to eat foods with high calories.

Does anyone know any foods that are high in calories but I don’t have to eat a lot of?

Any tips, exercises I need to do, any vitamins?