Suggest giving him a daily chewable children multi-vitamin because he is may not be getting all the vitamins and minerals his body needs due to his eating habits.
He doesn't eat and won't any veggies or fruits. He won't drink milkshakes or smoothies. It's ok that all he eats is chicken nuggets for dinner and P&J for lunches? He is always sick, has black circles under eyes, always looks tired and never has an engery. He couldn't even run 5 mins in a soccer game. That isn't from the diet?
His weight is just above the 10th percentile for his age which is considered normal. He is eating to some healthy foods, such as milk, grilled cheese, pizza, P&J sandwiches, Cereal (if not a sugar type) banana, breakfast items, and Mac & cheese. He may be a picky eater and that is all he will eat. Since he likes milk, suggest giving him milkshakes (ice cream, fresh fruit or frozen fruit – if he accepts it, and milk) or yogurt smoothies (yogurt, fresh fruit, and frozen fruit) for additional calories and protein. Remember to relax at meals and just give him the foods he wants. Slowly introduce new foods. Sometimes it takes 5-9 times to introduce a food to a child that they will accept, however, if they do not want it you have to not make a fuss and let it go. Hoped this helped you.