Hi I Had A Lower Left Back Pain In The

Hi I had a lower left back pain in the area of QL or even deeper to the psoas for about a week and last Tuesday I had a muscle spasm where I could not move and crying made it worse. The spasm stoped but it became very painful. After a few hours I was sitting and could barely get up and when I did I felt as if something tore. Pain continued and in the morning my abdomen started to twitch it felt like contraction (left side only). Today 4 days later my back still hurts, not as bad, and the twitching in the abdomen is in conjuction with the pain. Laying down on my back is when it hurts the most and in the morning. It feels better when I am active but sitting and laying down causes to hurt. I feel better and have been taking muscle relaxer. My question is which muscle of the back could be causing the twitching of the abdomen?