Assuming this isn't a disc problem and is just clenching, you might try upping your magnesium intake. Skullcap is a good herbal muscle relaxant. And keep yourself stretched. Meditation can be very helpful here. One of the problems with Xanax is, its short acting, and when it wears off you're back where you started. Rely on it too much instead of as needed and then you're stuck taking the drug all the time. Anti-depressants when they work are longer lasting, but be careful, they interfere with magnesium absorption so you can still get muscle tension. Gotta work on other things besides just medication when dealing with anxiety.
but yeah, exactly the same thing here. i fully relax, not even a min later i realize i'm all clinched, tensed, tightened, etc. which causes pain over time.
sorry i'm not much help here.
i always tense my shoulders and legs. oddly enough I seem to favor my left shoulder too. When I'm watching tv. I think i'm relaxing, then i rrealize I am nowhere close to relaxing and am very tense.