Swollen Neck Veins

   Last night, as I was lying down, I felt pressure in my ears, head, and neck (here, it was a bit of a tightening sensation down both sides). When I touched my neck, I could feel the veins bulging from under the skin. It was one vein on each side, both most visible in the hollow above my clavicle and then up the neck extending toward the jaw. It was worst when I lay flat on my back, but I could still see them when my head was elevated a bit---just up on two pillows. They’re not visible when I’m sitting or standing. When I sit or stand, the pressure in my head and ears lessens substantially. I cannot tell if what I’m feeling is a rush of blood to my head or related to my sinuses. I have bad allergies for which I recently visited an ENT—he prescribed Nasonex because of the abnormal mucous presence in my nose/sinuses. I just started the spray yesterday. He also felt my neck for lymph nodes—all were within normal range; he wasn’t concerned. I’d asked about when I push on the one lymph node, that I could see the blood in the aforementioned vein on the left side of my neck swell with blood even when I stand. He said I’m thin and the node just happens to be there, it’s unconnected to the vein and if I were to push like that on anyone, it would cause a swelling vein.
   I have been having heart palpitations since November. About a month ago, they ran a full blood workup, did a chest X-ray, three EKGs, an echo, and put me on a Holter Monitor. The blood tests, X-ray, EKGs, and echo all came back fine. I have a slight murmur, which no one seems concerned about—they said I have trace…something…and that it’s benign. They also said the monitor picked up PVCs, but that the structure of my heart is normal, so there is nothing to worry about. They think it’s perhaps caused by stress.
   Any insight into what might be causing my veins to bulge would be much appreciated.  I've read that this can be normal in people with thin skin when in the positions I was in, but I'm still curious.

[Cleveland Clinic]

It would be difficult to know for sure without reviewing your tests, but it ma be secondary to heart failure that is the backing up of blood behind the right heart. It also may be secondary to a valvular regurgitation ( tricuspid regurgitation) or an arrhythmia ( that is the beating of the atrium against a closed tricuspid valve). Ask the physician that reviewed the tests if he can based on your prior tests differentiate between any of these causes.

[JessM2307]

I don't quite understand.  If they read the tests as they should've read them, then wouldn't any of those problems you mentioned show up?  I would think heart failure, serious arrhythmias, and regurgitation would be clearly visible on the echo and Holter results, no?  You mean secondary as though I might have those problems already and they're subsequently causing this neck issue, correct?  Please clarify.  

There are no other possible causes of my seeing these veins?  And only when I'm flat or close to flat on my back?  I can also see it when I'm on my side, but only the vein on the side of my neck and is nearer to the surface I'm laying on.