I have severe pain in what i think is my erector spinae...? the muscle(s) will contract and get very stiff and won't relax for hours. causes/cures?

Musculoskeletal pain: You are describing significant pain and spasm in your back muscle. This is almost always related to primary muscular strain. It does not sound like a disc problem. Stretching, heat and massage would all be helpful. If you're doing some athletic activity or workout, this may be aggravating your back. Be careful with proper lifting mechanics. Do you have a new mattress? Pillow between legs at night.