I used to be scrawy. You’re eating about half as much food as a scrawny person needs. And you’re eating almost all garbage. In short, you’re starving yourself slowly.
This is what you want to eat:
Breakfast: 3 eggs, 1/4+ lb bacon / ham, 2-3 slices of toast with a liberal smearing of PB & maybe some J. Maybe some potatoes. Definitely a whole orange, apple, or banana, or an equivalent mound of berries. Plenty of water. No soda. Maybe some fruit juice, but check the label; you don’t want thin food-colored HFCS, yuo want the real thing.
Lunch: A 12" sub & your favorite chips. Or a bowl (not cup) of serious thick soup / stew and a half monster-thick sandwich. My homemade turkey or ham sammiches are about 5" tall, and it’s all meat & cheese with a couple layers of lettuce & tomatos. They weigh over a pound. Not like the crap from subway which is white bread & shredded iceberg with 1/2 oz of fake cheez in it.
If you like burritos, try a Qdoba or Chipotle. One of those is almost a decent lunch in terms of both size & content. You can make them at home for almost nothing.
If you want pasta, have a lasagna; not a smidgen of spaghetti with ketchup on it. A real one filled with meat & cheese & real tomoatoes, 8 oz or more. Have a big salad as well.
For a change of pace, go to any fried chicken joint. Get the 8 or 10-pack of chicken with no accessories. They’re loss-leaders & usually real cheap. Eat 5 or 6 pieces for lunch & save the rest for later.
Have an apple, orange, or banana with whatever else you ate. No soda. No sweet dessert. Plenty of water.
When you’re hungry again at about 3pm, eat a power bar.
At 6pm it’s dinner time: 12+ oz of meat or fish, a hefty salad with not much dressing. A whole baked potato; two if they’re small. Real sour cream is fine; so’s butter. Avoid fake crap like “low fat” or “lite” anything, or margarine. At least 6 oz of real vegatables. Get some beans / peas in there a few times a week, maybe in lieu of the potato.
if yuo can find a place with a decent soup/salad bar, do that once a week. 3 plates of salads (not all the mayo-encrusted crap; real greens), and 2 bowls of soup oughta do it.
Skip dessert. No soda. Plenty of water. No post-dinner snacks except maybe some berries or couple bite-size chocolates.
That was me at 5’10 and ~130 lbs. From age ~14 to age ~40. Every day, unless I was really hungry or working out hard. Then it was more.
Things to note: almost no sweets. Almost nothing out of a box, except at lunch when you’re away from home & have to settle for restaurant cooking. Not much white bread. Nearly zero “empty” calories. Not avoiding fat, but not really seeking it out either.