I also wonder how much handling you are doing with this snake? All new snakes should not be handled until they've fed easily & reliably for 3 times
at regular intervals, at least, & for best results. Remember that just because a snake is docile when handled does not mean it isn't stressed: anything
that picks up a snake in the wild is normally a predator that's about to eat it! Most of our snakes do learn in time that they are safe with us, but that
is going against their instincts. So if you've been handling this snake, you need to back off while he does some more growing & feeds consistently.
You should be feeding him at night, if you aren't already doing so. That's his natural time to hunt. Many snakes are put off by too much light or by us
"hovering" during the feeding process also...just offering possible suggestions here, in case. What kind of hides are you using? (some are too "open"-
like those half-round hollowed tree bark things; some are just too big & don't offer "back pressure".)