I have head and neck pain that seems to ony come one when I'm standing. Once I lay down for a bit the discomfort goes away. Why is this?

Standing neck pain. Usually pain while standing is mechanical in nature. Nerve pain for example can occur regardless of position. Muscles are more likely. Also your neck [position while standing can be the culprit. Weight bearing can be painful if there is a disc problem. Lying down relieves this pressure. You should see a physician for proper evaluation.