awwwww ,kittens do need a lot of sleep
but they do play alot too ,all of my cats when they were kittens were all manic ,lively and running all over the place like loons
but bobby is very small and week so maybe thats why he is needing more sleep
if it was me id get him checked over by the vet again and the vet will be able to put ur mind at rest as to wheather he/she thinks its normal to be sleeping that much .