If severe constipation/no bowel movement all returns after taking citrate of magnesia and successfully having 2 to 3 bowel movemens what could this be from?

Poor colon strength: Regular comfortable bowel emptying requires the assistance of large intestine wall muscles & your belly muscle pressure. Chronic constipation can weakens these muscles & the large bowel can balloon out, reducing their effectiveness even more. It can take a year of stool softeners/scheduled daily or multiple daily emptying to correct this. Failing to treat long enough is the main cause Rx will fail

Fiber and water: Agree with Dr. F . To have regular bowel movements requires sufficient fiber and enough water. You may take a fiber laxative like Metamucil and drink enough water daily so that your urine is colorless. For the long term you may try to increase your intake of fiber foods. http://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/high-fiber-foods/art-20050948