I have a pulsing pain in the left side of my neck that i only feel when im standing and it hurts more when i inhale, could this be serious? i

Unusual: Since you state that increasing your intrathoracic pressure makes you have a sensation of blood vessels pulsating or backing up in your beck - it is possible you have a chest mass in the medistinum. This should be seen by a doctor. Maybe it is just your jugular vein? It is more usually see to distend when you do a vlasalva maneuver - which is to increase intrabominal pressure. See a doc.