Left side neck/jaw veins enlarged

Hi all. I’ve been trying to find the root of my constant dizziness, lightheadedness, and shortness of breath for over 1.5 years now.

Over the last 2 months I’ve noticed a prominent enlarged vein or muscle on the left side of my neck (where pain/tightness is). It runs from my neck up to the lower joint in my jaw, and then out back below my ear.

I notice it more when moving my lower jaw to the left side (side it’s on).

Is this a concern? I’ve had CT and MRI that showed nothing but a thornwaldt cyst (benign) but I’m starting to think this could be the cause?