Well, here’s what he should be eating:
lots of hay, roughly an amount his own body size everyday. Does he have constant access to hay? Do you have a litterbox for him? Putting hay in there helps.
A small amount of pellets, depending on body weight. I’m surprised he doesn’t eat them, though. What kind of pellet is it?
A mix of greens, roughly 1-2 times the size of his head.
And occasionally a small amount of treat! Carrots are full of sugar and should be a treat, he should not have 1-2 carrots a day, haha! An amount the size of the top of your pinky finger is about right.
I would guess he’s filling up on carrot and that’s why he doesn’t want other things. Hay is very important, so I suggest to limit his greens (and carrots!) and see if that helps encourage him to eat more hay. You can also try and stuff hay into cardboard tubes or boxes to make it more fun for him.
Have you taken him to a vet yet to be checked over? Edit: oh sorry just saw you said about seeing the vet next week, nevermind!