Well to say I am confused is an understatment!
Why is kitten milk the worst thing and cottage cheese wasnt mentioned but lacto free cheese and thought it was lactose that was bad for some cats.
Such a young kitten needs to eat anf if its losing weight that is very bad.
It could be by mixing the meds in the food that has stopped him eating cat food cos he thinks you have tried to poisen him.
I would try the fishy food as suggested by Emmy below, no meds in it. If the diahrea keeps on then there are som capsules called.........umm just looking cos saw them yesterday...........Synbiotic D-C Protexin veterinary. It was given to me for my 10month old kitten Lupin who had diarhrea for a long time and if I nremember you open the capsule and put half on the food twice a day but dont have instructions.
All other meds he either wouldnt touch or they did not help him.
I was lucky cos he would eat the special food, well for a while and he finally got better. The first normal food I tried him on cos he stopped eating the special one, was Tesco chicken in jelly pouches and he was fine,,,,,,,,,,,,,we graduated onto Felix jelly pouches and Sheba tins.