I have similar responses to anxiety- I can feel my heart racing, acid reflux causes me to vomit at high stress times and i feel I am going to vomit quite frequently. I carry a lot of muscle tension d/t stress/anxiety as well. My traps are tight and can cause headaches, my neck is killing me much of the time, and my shoulders as well. I get knots along my scapula on both sides and frequently get knots up and down my spine, I know some of this is because of physical reasons, I have improved with lots of stretching and some changes to my work station, but stress seems to be harder on it than poor ergonomics. I have found a better treatment than muscle relaxers or chiro care is taking a few days off work (a major stressor for me right now) or massage which allows me to relax physically and mentally.

I hope things get better for you.