I Have A Giant Swelling Vein Or Artery In My

I have a giant swelling vein or artery in my neck that pulsates then goes down then comes back again this is the second time this has happened to me and this time it has been doing it for over an hour..what is it and should I be extremely concerned...my doctor is aware and didn't seem concerned when I call I am just worried because it is so close to my head