I would suggest starting solids if you aren't already (I didn't catch it) my LO is just like yours. Very low on the charts and a voracious nurser and I would guess he is just not getting the calories he needs/wants. Now, my LO will eat three times a day (ridiculous amounts, about what I would feed my seven year old) and she nurses about every 3-4 hours.
Almost all typos provided care of my iPhones stupid auto correct
"Honesty without compassion is just unrestrained hostility..." ~ Kelly ~
Mother to Az-man (01/05) and Annie-Mayhem (12/11), Wife to Jon and Empress of the Home