E.J.
My son did this and it was SO hard. I hardly even want to answer this b/c he is 6 and just now finally learning how to eat age appropriately. It's so so hard. A very good book for it is "Just Take a Bite"
One hard thing for me is that people didn't understand. They'd be like, "He just doesn't eat?" Yep!!! We still don't have an answer for why he didn't eat. A healthy kid but he failed to thrive. It became not about why, but about how can we get him to eat?
Good luck!!! The book is really really good!!!