Well...no dogs like taking pills .That's a fact ! I can only suggest that you give him time .You say you have had him two weeks.If he is happy with the dry dog food and water then all well and good. I. feed my dog the same.Varying it with sardines ,white fish or tuna.As long as he is eating his food and has regular mealtimes he should soon start to put weight on.A dog won't starve himself through choice.Have you tried some doggy treats.We give ours chewy sticks ,Bonios and Markies.Give him time and just keep offering different stuff. With a lot of love and attention he will soon catch on.He has probably just been given the same diet all the time before you took him on and thinks that this is all there is.Make a fuss of him when he does swallow the pill and tell him how good he is.I am sure with time he will be O.K .If he seems traumatised perhaps a dog psychologist could help you:..perhaps your vet could recommend a good one.