Is it ok to take Two Percocet 7.5/325, every 4-6 hours?

I have been having really bad back pain.and i go see a pain doc regularly and goto physical therapy. I have degenerate disk disease, Arthritis, scoliosis, and a bulging disk. .So my doctor prescribed me 1 percocet 7.5/325 every 4-6 hours. But it hasnt really been helping. Until I am able to speak with my doctor is it safe to take 2 every 4-6 hours. The nurse said yes but was just wondering what u guys thought! Thanks so much!