Is it possible that holding a bowel movement in could cause a stabbing pain in the center of chest between breasts?

No: Valsalva maneuver, or bearing down, holding of breath increased intrathecal pressure, intra-abdominal pressure, which can cause diffuse esophageal spasm, or pain due to esophageal etiology, if you have pre-existing conditions which predispose you to have such symptoms, including: hiatal hernia, achalasia, reflux esophagitis, esophageal dysmotility. However, cardiac causes needs to be excluded.