Could my bed be causing chronic shoulder pain?

A few months ago, I had some pretty severe muscle tension in my upper back that radiated up my neck and around to my chest, causing sharp burning pains in my breasts. I saw a doctor that said it was stress-related muscle tension and gave me prescription strength ibuprofen and a mild muscle relaxer. Neither did much good but the pain eventually went away – well, mostly.

One pain that never fully dissipated is in my right shoulder. It’s in the muscle near the center of my back and there is a knot there, but no amount of rubbing makes it go away. It just recently started getting worse and is particularly bad at night and early morning. It hurts to lift my head off the pillow or roll over, so I’ve had some restless nights. It feels only mildly uncomfortable during the day.

Our bed is kind of old and just started making creaking noises, but still feels comfortable to me. Could a mattress be causing my problem?

I’m not experiencing a whole lot of stress at the moment and I haven’t injured the shoulder, so in not sure what could be causing this. I don’t want to see another doctor just to be given more muscle relaxers that don’t help.

Should I be more concerned about this? What can I do to alleviate the pain, other than getting a professional massage (no thanks)?