I really suggest that you get it looked into or at least see if you can get some good qualified phys therapy - I'd hate to see it develop into a chronic RSI or TOS type of thing. I should have mentioned that if you having to use/wear the brace for 5 yrs isn't a good sign.
Just off and on I hope- occasionally??

upper body posture & alignment is something to be aware of too.

shoulders = rolled forward? hunched? uneven?
head = often tilted, angled, jutted or carried forward of the body?
someone may have to help you check your alignment from the side.

the last post in out TOS sticky has a link to some posture & therapy videos
http://neurotalk.psychcentral.com/showthread.php?t=84