Hello community of experienced snake owners! I have quite the problem that I feel is unique to Pip, my axanthic ball python from petco (first problem right there I know.)

I got him in March of last year and they told me he was hatched a few months before, which makes him atleast a year old by now. Though he only weighs 50 grams, 60 since I took him to the vet a month ago.

Pip never had a problem eating, EVER. I'd feed him one fuzzy per week, and I tried 2 in one week but he wasn't hungry. I, nor he, has ever missed a feed, so I promise I'm not malnourishing him.

His Temps have always been fine, though it took about 2 weeks of tampering to get them right. He's at about 85 hot spot and 75 ambient, though now that winter is setting in, the Temps are fairly cold at night (working on a solution).

I've always been concerned about him being sick since his poops have always been a white liquid with a little tiny turd looking specimen accompanying it..I've had OCD about poor little Pip since I got him. I took him to the doctor once I realized he definitely was not gaining weight and that a hatchling weighs more than he does!

Hes only shed twice since I got him, both times it was super stuck and he was wrinkly and dry as a corpse. I feel so bad. The vet tested him for parasites and it came out negative, however he gave me a dewormer anyway alongside antibiotics. After faithfully injecting him for a month, he's gained 10 grams.

TLDR; 1 year old snake is 55 grams halp.

I'd be more than happy to provide answers to questions, I just need help understanding this problem. Thanks