question

i have a vein on my left side of the neck (not the right side at all) that bulges somewhat when i raise my left arm or move my clavicle on purpose. i can see that the vein is much more superficial on that side compared to the other side. i say this because i can se where the vein is even when it is flat. also if i put my finger on it then it bulges too as if im blocking it. im pretty sure that this vein drains blood since when i cover the top nothing happens but when i cover the bottom it bulges. i was told by a vascular doctor that it is the external jugualr vein since it goes somewhat perpendicular to the sternomastoid. also heard that thin people with bigger neck muscles tend to have this sometimes and its normal. i recently lost weight  and thats around when it happened. i went from 165 to about 153 or so. im in my 20s and have no other symptoms (no chest pain or shortness of breath etc..) or pains. i dont know what this could be but im kind of worried that it could be something to do with the heart. when my physician listen to my heart he said it was normal he also listened to the veins in the neck with the stethoscope. ive also had an EKG done and it was normal. i dont know what to think. please help me out. thanks a lot,