Not sure if it will help you, but when I'm racing on the inside and feeling simultaneously trapped or immobilized, it helps for me to slowly push against something with my legs...honestly, I love pushing against my car and imagining I will tip it over (maybe some day!!). Or push slowly against a really heavy piece of furniture or a wall. Or use resistance straps somehow and push with my arms or legs. The slow exertion helps settle the "charge" a bit without further amping up my heart rate or arrhythmia that sometimes comes with lots of stress. Then, if I can do that a little, it helps to go for a walk to feel that I am not trapped or immobilized...like I need to remind my body of this. Basically, finding a way to move safely to tell my body it's okay.
Distractions help under less stress (artwork, movies) but when feeling really compressed and trapped I usually need to find a safe way to release some of that energy or stay connected. Squeezing my arms or feet without hurting them helps sometimes too...or alternating between pushing against something and curling up tight in my favorite corner and "hiding." Go to the hospital if needed. Glad you can talk to your doctor soon.