It could be from triggerpoints too.
It's like a small knot{& very tender sore spot} in your muscle.
I even get them on my scalp.
Once I relax and do stretches they usually go away, if not then I do the trp pressure release on them.

you can experiment if you find sore spots to see if it helps or not.
there are a few places not to use pressure unless you are experienced (mainly arteries/veins and small bones in the throat)
read the links below for more info

Triggerpoints, referred pain and stretching info:
http://www.triggerpointbook.com/index.html
http://triggerpoints.net/_sgg/m1m1_1.htm
http://www.pressurepointer.com/pain_reference_chart.htm (this one uses a graph with clickable links and easy to understand}
http://altmedicine.about.com/library...ressure+points
http://www.drlowe.com./triggerpoint.htm
http://www.erikdalton.com/articleduramater.htm
http://deeptissue.com/articles/articles.html

When my RSI/TOS hit at the beginning I had bad dizzy spells, nausea & total fog brain - I was thinking "am I getting Alzheimer's, ADD and speaking problems all at once??" It was bad!
In my case I think it stemmed from the vertebral artery being affected by muscle spasms.
- because after good PT and off work those problems faded away.
My voice is still affected as far as singing - it is weak and falters after 3 songs or so.
http://tos-syndrome.com/newpage12.htm