wrinkled skin

also how do i know when to upgrade him to a small mouse and so on?

so how do i know then when to upgrade him to a small mouse and so on? also since hes too skinny is he in dangerous health or will he be okay once i feed him a few times?

Weigh him and follow that chart I posted earlier. A kitchen scale will work.

Poor baby is just skinny !

Since he is willingly eating, he should plump up in no time at all :)

Don't feel bad, you got bad advice from the store, but you came here seeking answers after you got concerned.

He will go into a shed cycle once he gains some weight.

Is it the snake in your avatar?

If so, then the mouse pinky was basically a starvation diet.
Don't feel bad, though, you came here for help and your snake will recover.

The snake is probably pretty light weight for its length and age, but you don't want to overwhelm his system by feeding him to much all at once.

Usually, you pick a rodent that is about as big around (if you visualize it stretching out, the thickness around the middle of it, its thickest part) as your snake is at its biggest part (middle).

Your snake is skinny now, so work your way up slowly. If he was eating mouse pinkies, try a hopper next time, or go straight to rat pinkies. If he eats well and gains a bit, you can work your way up to the correct sized food. I think that would be small mice or rat fuzzies, possibly rat pups.

Try to weight your snake. Use grams, its easier to keep track off then pounds and ounces on something so small. You can check on weight gain this way, plus once you know the weight you could give us a better idea on his actual size. Could you perhaps make a better picture of him in your hands, or next to a coke can or something like that?

I can't believe they told you to feed mouse pinkies once the week :( I start my hatchlings on mouse hoppers, and that rapidly goes up in size.

He will be alright, though. They are tough.

I forgot to add, while you bring him up to a healthy weight and size, limit handling. His body isn't used to digesting larger meals and it will be working harder during recovery. Best not to stress him much with handling. If you do have to handle, give him a sold 2 to 3 days after eating before you pick him up. Also, make sure your temps and humidity are spot on.