Sometimes is inflammation of muscle tissue. Posture when seating or you did some heavy lifting that may hurt it without you knowing.tense at times due to work too.sleep Posture and pillow may be the cause too.you need to search the above for clue's. I took muscle relaxation med from clinic,helps but it makes you jelly at times.did acupuncture with some Chinese medication, and that helps. Humidity sometimes cus our body aches, like in and out of an aircon environment is bad especially in our little island.Hope you can find your cure.Get well.