The last few nights I've woken lying face down with a painful back, almost like a tight belt. It's relieved a bit with stretching. However, today I just can't yet rid of it. It's like a tight belt around my lower bike. I can move but it really hurts. It's definitley muscular, when I woke last night it was like my lower back had seized up. I've never had this before. Has anyone got any suggestions on what to do.