I was involved in a car accident a few weeks ago, and my neck has been getting worse. my whole upper back, neck and shoulder area is in constant pain.

Neck pain s/p MVA: Go to ER today.It may be spasm ,as that is sometimes delayed and if not treated promptly can get worse but you want to make sure it is not a fracture of the vertebrae that did not appear initially ( it can be missed) .If it is a herniated disc you will need an MRI to diagnose. If not fractured consider NSAIDs( if no allergy) , muscle relaxants ,epsom salt baths ,PT. Go to ER today.