Aww don't feel bad or guilty. We do the best for our babies, and the fact that you noticed the limping and took him to the vet shows you love and care for him. Hopefully the meds will help, and it will pass. Maybe he is just stiff after lying in one position for a while when he sleeps, or maybe it's the position he's sleeping in that is causing his leg to either fall asleep or be stiff when he wakes up. Keep us posted on how he does on the meds, and don't worry too much.