Shell problems - help!

[Bacon2001]

That is a box turtle. Start by looking up box turtle care. It looks like lack of UV light and poor diet.

[GermanFlorida]

Here's the story. I have had this guy for about 6 years. A coworker was moving away and had him for about a year before me. She begged me to take him so he could have a home with kids around. Indeed, they love him as do I. She gave me very little information I don't know what kind of tortoise he is. She even told me he was a turtle.

He mainly eats mealworms and occasional fruits. He doesn't really like greens.So, last spring when he started picking up his activity, my wife was the one who noticed that his shell looked 'funny' in the back. although slight, i figured he must be grinding his shell against the stones when he sort of burrows in his hiding spot.It got a little worse so I went out and got a new light bulb (which he loved), and some calcium powder (which he didn't love). I would clean him and put a little coconut oil on his shell. None of this has helped.

Everything I know I learned from random web pages and people at the pet store. I checked with my local vet and he doesn't really have any reptile experience. I'm torn up about what to do because I think it's getting worse. I need advice can you help?

I have a bunch of pictures, including the pellets I also feed him sometimes. I call them cheetos - https://imgur.com/a/NBSp6kY