Bad eaters - vitamins?

Mi

I'm so upset. My son sucks at eating lately :( I have read over and over again not to give in to them, that they will eat when they're hungry, but he WILL NOT. He will go a whole day with no food, cry his eyes out all day, lay on the floor exhausted because he is tired... and I am just not willing to see how long we can go on like this so PLEASE don't tell me to starve him until he eats healthy options.

Anyway, I often try 5 or 6 meals until he wants something. He's picky with texture, spits out the textures he doesn't like, and what he liked this morning he may not like tomorrow. He's terrible. Generally, Easy Mac is something he enjoys, and he also likes yogurt pouches.

Oh, and he has decided he's a vegetarian. I used to be able to at least give him a chicken nugget, but now he won't even eat those.

I worry that there's no protein or iron in his diet. He's allergic to eggs, so I can't give him protein that way. Do any of you give your children vitamins or pediasure to supplement picky eating? I worry so much that he is just not getting what he needs. He's in the 80th percentile for height but only 35th for weight currently.