Last Evening I Developed A Dull Ache On My Left

Last evening I developed a dull ache on my left lower quadrant. When I sit down or lay down I have no pain. When I first stand up I have a dull pain for a few minutes then it goes away. Almost like a muscle pain. During a bowel movement the pain gets sharp for a few moments then it goes away. No fever, no nausea, good appetite and no weight loss. My doctor feels that its a muscle problem