Toddler Formula

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My 14 month old has a milk sensitivity. She had to have a sensitive formula since she was born. (She would projectile vomit every feeding and we switched to a sensitive and she never even spit up once) At her 12 month appointment pediatrician told us to put her on whole milk. So we did and we started weaning her like we were supposed to and at a 6ounce formula to 2 ounce milk ratio she started projectile vomiting and had horrible constipation. So we switched her to lactose free and started weaning all over again. After being on 4 ounces of formula to 6 ounces of lactose free milk her poop started getting really hard again. So we have her more water and fruits to compensate. Well now that we completely transitioned to lactose free milk she will not drink it at all. She hates it, but she will down a formula bottle. We’ve had to pour out so much of the lactose free milk and that stuff isn’t cheap. So husband and I were thinking of starting her on a toddler formula. She eats a pretty well balanced diet. Fruits, grains, meats and veggies but she doesn’t eat a whole lot. So we are concerned and want to make sure she’s getting enough to eat. Does anyone recommend a toddler formula? Or should we give her pediasure? Or something else? I do not like the idea of giving her chocolate milk (which makes her projectile vomit and constipates her anyway) and the nurse practioner we saw last time told us she would be fine 🙄