Hi Melissa,
I am very sorry about your pain!
I seem to be having the same problem, although not as intense, adn I am only 20 years old. Like you said, the pain is in my middle back, on the right side, right under my bra strap. I have been having it for over 3 months now, and it is not usually too bad, but it has gotten worse!!
I talked to my mother's boyfriend who is a doctor, and he said it could be my bra! It seemed very strange to me. I am heavy chested, and tend to wear cheap bras since I don't have the kind of money to go to victorias secret. He told me to buy an expensive, supportive bra and that might help...
Otherwise, he told me it could be muscle spasms, which could be helped by muscle relaxers.
I would talk to the clinic about possibly recommending a specialist. I know it can be expensive, but with the kind of pain you are having, I would imagine it might be worth it.
I hope you feel better! If my pain doesn't go away in the next month, I am going to see a specialist. I will let you know what they say.