Debbie,
i think aiden is doing fine, just keep an eye on his wet nappies, as long as they r coming out then he isnt dehydrated.
A lot of the time bubs loose weight the first week or two so he might have put on more than you know.

i know ashley is piling it on! lol
birth - 2.66kg, 4 weeks - 3.82kg, 6 weeks - 4.04kg