My neck back and chest muscles are so tight that I pull those muscles just sitting at my desk somehow. What are some good stretches to prevent this?

Need expert instruc. This sounds like a muscular problem make an appointment with a physiotherapist. I'm sure your family doctor can recommend someone for you.
Check out these. Links. Taking tylenol (acetaminophen) or nsaids (motrin or aleve ) should help.Hope u feel better soon!
My own experience. Try some heating pad on the neck, then do some exercise on the shoulder blade muscles- a few sessions with a trainer may be worthwhile to improve your posture. Try to get up for a few minutes and stretch for every hr you spend at the desk. I am sure there will be many more suggestions from others in this panel.