here's a guide i found:
Mouse size/feeding guide (taken from the Munson feeding plan):
Snake (4 – 15g) = 1 Pinkie (0.5 – 3g) - feed every 4 to 5 days
Snake (16 – 23g) = 2 pinkies (3 – 4g) - feed every 5 to 6 days
Snake (24 – 30g) = small fuzzy (3 – 6g) - feed every 6 to 7 days
Snake (30 – 50g) = fuzzy (7 – 9g) - feed every 6 to 7 days
Snake (51 – 90g) = fluff/hoppers (7 – 12g) - feed every 6 to 7 days
Snake (91-170g) = Small Adult/Weaned (13-18g) - feed every 7 days (Includes medium mice 16 - 20g)
Snake (170g+) = Large (19 to 25g) - feed every 7 to x days
Snake (400+) = X large (30g +) - feed every 10 to x days
looks like i've been underfeeding.

i will definitely start beefing up his diet come next feeding.