Sorin Needs Medical Care

Sorin is a bearded dragon I rescued from Petco in April of 2013. He was in a viv smaller than a 20g long with 10 other beardies all about 10" long and a pooped filled water dish. Around May/June my boyfriend and I noticed that Sorin was having trouble with his back left leg. We've taken him to the vet multiple times, done two treatments of shots (throughout this the pain was switching to different legs), and just when we thought he was getting better, his back left leg started having trouble again.The vet orginally thought it to be septic arthritis, but now is unsue. She wants to run a few other test that would total up to $450. Any ammount that you can offer would be much appreciated. My boyfriend and I are working part time jobs while going to college and paying bills. I want to be able to get the blood test by the end of next week. Any help would be greatly appreciated. Thank you, everyone.