I have a pain under right rib (last one where it attaches). i get it while seated, began at work. goes away when i lay down. ?

Muscle Spasm: Yes this usually is a muscle strain. Can be poor posture, vitamin and mineral deficiency affecting muscle function, lack of exercise, weak muscles, obesity. You could try improving your posture at work, stretching exercises, massage. If nothing works then see a Doctor.

See below: Pain under a rib that goes away on lying down could be related to some local temporary condition such as a muscle strain or possible inflammation of the costochondral junction where the rib attaches to cartilage. If the area is tender to light palpation it suggests a local condition as above. To be on the safe side, if the pain lasts beyond several weeks or is rather severe it's best to see Dr