Its more like to be what he has eaten making the sick brown I think'
It could be there is too much paste and if so that could make him ill. half a capsule of protexin once a day is all he needs at the most. So you need capsules from the vet not this bloomin paste!
I think that strict watch must be kept on the little man and he must have enough of his special food and know Lupin used to try and steal food from anywhere but if not left temptation he will eat his own food. Dont forget and leave biscuits in his reach.
Another thing that can make him sick is if he is starving and gobbles his food too quick.
Meals need to be small and often and Sheila is so right about the stress.
I think the best way to gauge how well he is, is by how he is acting and if he is playing and running around. If he is doing this and eating and drinking he is more like to be Ok.
You need to try and stop worrying and try and keep him from the vets for a while to allow him to settle.....you can ring the vets to get protexin capsules.
He is possible extra hungry cos he really should be on kitten food but cant be at present.
I know just what you are going through cos I was there with Lupin but he was older and bigger than little Nemo but it was still a worry.
Try and relax and give him lots of cuddles