Seems like my lower back has tightened up to the point where i have to lie down. i'm active and not overweight. is this what they mean by throwing it out? all i was doing was throwing a frisbee.

Maybe: Most likely you have a muscle sprain in the back. Although you are young and active, you may have to get checked out for spine dislocation or other injuries if the pain is severe or you develop nerve damage. Or if the pain persists longer than a month.

Yes : Sounds like you have severe muscle spasm. I would recommend a short period of rest. You need to get into physical therapy to help relax the muscles. Anti-inflammatory medication along with a muscle relaxer could help. See your doctor for this.