Baby snakes in general are voracious eaters. I imagine that he may just be hungry. I'd suggest feeding him more often, maybe every 4-5 days instead of 7. I feed my baby balls and my baby carpets that often and they are doing great. I have never had a baby burmese, but judging from their adult appetites it's also possible he would eat more than one mouse at a time.
See how he does getting fed more often and go from there.
Good luck with your baby!