elderly lab

Question
Hi, I have an elderly (14 years old) lab who is in pain in her hind end and has been on Rimadyl for some time.  Also, lately she has started panting very heavily and constantly.  Because of the panting, which was a new symptom, we took her to the vet who did x-rays of her chest and did bloodwork but nothing was found.  In the last two days she has stopped eating and we are taking her to the vet today, but I am wondering...
Shouldn't the vet be able to do more to relieve her pain?  
Could the panting be because of the pain?

I am very worried and sad that she is suffering.  Yet, she enjoys enough of her life that I would like to help her to live as long as possible, but just with less pain.

What do you think I should do?  Should I get a new vet or take her to a large vet school hospital such as Tufts?

Answer
If you can, Tufts might be the best idea.  Few vets in private practic have the resources a large teaching clinic would.  I had a friend whoise dog lost its vision, and she was driving a couple of hours to our state school.  

It is really tough.  We were about to put our 14 year old to sleep, but a new pain medicine has bought her some time.  She is doing well enough I will have her at a booth all day tomorrow.  I will drag her bed along to keep her old bones off the concrete floor.