Firstly, keep on with the painkillers.
Secondly, go to the vets about half an hour early and make sure you take your pup for a walk BEFORE you go to the appointment. You are going to have to be cruel to be kind. You need him limping/not weight bearing on that leg prior to the appointment so do whatever you did before when he started to refuse to put weight on that leg.
It may be the only way you can help you pup, but sometimes these things are not obvious and you need the vet to physically see the problem. They get to see a lot of over protective owners worrying about the slightest thing and from their point of view, they can see nothing and find nothing, so show them the problem. Walk your pup immediately prior to the next appointment so that he his limping when you arrive at the appointment and allow the vet to see the issue.
