Four month old ball python only 83 grams

[lizzybit]

Hi! I'm new to snake keeping, which means for me that I've spent hours researching and effectively absorbed all the worst case scenario information that was out there. Which makes me a little jumpy with my new boy, Noel. I got him Oct. 31, and he was a few days past 3 months. He's three or four days past 4 months now. He refused to eat for THREE WEEKS after I brought him home, and with his breeder's help, I tried a lot of options. He finally started eating when I offered him a live hopper mouse, which I know he shouldn't stay on, but the priority was to get him to eat in the first place . His husbandry is perfect by all the standards I've found online-- he's in a twenty gallon with ReptiBark. He has a couple thick climbing sticks that he likes to chill on. He has a 91-93 F hotspot that fades into a 72-75 F cool side. His humidity stays steady between 60%-70%. He has hides on either side, and a water bowl refreshed every day. I've been feeding him one live hopper every seven days on Wednesdays. I'm going to switch to every five days and feed him next Monday. I'd like to get some weight and some feedings under his belt before I switch him to ratties because he seems to be a pretty stubborn idiot about his food. He is very clearly underweight. I weighed him yesterday and he hovered between 83 and 84 grams. I'm very concerned about him. Any advice is REALLY appreciated.