For a 3 y/o, I would just stick with a 7 day schedule and let it grow at it's own rate. At that age, it won't be hitting any more growth spurts like a juvenile would. Trying to feed too often may cause your snake to go off feed for a while after it gets enough to eat. You can try feeding it larger meals, but the more you feed, the more time they need to digest it. Have you tried switching to rats?