I took 2 bottles of magnesium citrate yesterday plus lots of water as instructed my gastro doctor and still have not had a bowl movement!!

Enemas are helpful: If you have not had a bowel movemt yet I would also give yourself an enema. I am unsure what the indication of the mag citrate was for ( colonoscopy cleanout or therapy for constipation) but I initially always recommend an enema to be given rectally if you have not had a stool for a few days prior to the start of drinking the solution. This may solve your issues. One adult size fleet enema (sodium bisphosphate).