Baby Ball losing weight NEED HELP

[Bogertophis]

Pinkies are too small for him, it's not enough food, poor snake. I know you meant well but a new snake keeper getting a snake that's not feeding isn't a
great 'recipe' for success...but we'll try to help you all we can, unless you'd rather return him to the store. Honestly they shouldn't have sold him to you.
And there's no such thing as a snake that's "too young to eat on his own". Shame on them! If you keep him, it won't be easy nor can we guarantee your
success.

First: Have you checked him thoroughly for mites? wipe him with a damp white cloth & look for tiny moving specks, also check in his water bowl. You
should use plain white paper towels on the floor of his cage also, so you can easily check for mites or any other health issues (like bloody stool, etc).
If you find mites, let us know ASAP (unless you return him to the store, obviously).

He's in trouble with not enough humidity also...first thing, give him a "humid hide"- buy a plastic food container w/ snap-on lid that's large enough for him
plus a good supply of sphagnum moss (so probably 3-4 times his size to allow for the damp moss). You can use a very damp small towel if you can't find
the moss quickly (for now). Cut a doorway into the lid of the plastic container that's more than big enough for him to enter & exit easily.

How are you keeping him, anyway? To best help you, we need to know about his caging & temperatures (hi, low, ambient), kind of heat (regulated how?) etc.
How long have you had him? What is his hatch date? (his exact age?)