muscle/organ stiffness & burning

About 1 month ago, i began getting muscle stiffness and burning (primarily on the left side of my body, arm, leg and neck). The muscle stiffness/tightness may persist as little as 5-10 minutes to as long as a couple of hours. It also feels like these types of symptoms are occurring in my organs (lungs) and particularly acute in my esophagus (near the adams apple). The organs feels like they tighten up then relax again, while muscles on my chest tighten and in my arms muscles burns or tighten. At times, i feel like i am slurring my speech from this, but then it will disappear. Lastly, typically the veins in my hand are visible, but i have noticed that they now disappear and my wedding ring can slip off my finger (and in the morning be difficult to take off). What started out as intermittent headaches last April (onward) seems to be becoming a bigger issue. I have lost some weight of late, but it may be due to the anxiety (unsure).

I have now visited several different doctors, with no real answer except for stress and acid reflux. Needless to say, i am worried and trying to figure out whether this may be neurological or something else. I am curious as to whether these symptoms are more neurolgical, vacscular, virus-borne... anything?