What Causes Popping Noise From Behind The Head?

Hello this has been goin for over a year now , but i have this constant poping noises from the veins on the back of my head whenever i open my mouth and when i tilt my head a certain angle but i t does it really no matter what. Not only is it really bizzare to me but its like i can feel high pressure though those veins and it irritates me very much. I find it very unsual what is causing this and is this serious????