Pain for couple days in left side of back. hurts a lot when i move, tense up my muscles and take deep breaths. pain is sharp. what can this be?

Muscle strain: You may have strained some muscles in your back. Now when you stretch then you feel the pain. Try a non steroidal like ibuprofen.

Low back pain sharp: Low back pain is commonly associated with irritable bowel syndrome which can sometimes be improved by having a bowel movement. Also, consider any aggravating factors such as exacerbation of the acid reflux disease or worsening anxiety symptoms that can contribute to direct pain or referred pain. Lastly, as can happen in anyone, low a simple muscle strain or pull can cause pain and spasm locally.