I took half a bottle of magnesium citrate per doctors orders and nothing happened. i took the rest of the bottle today and still nothing. now what?

It takes time: You must be terribly constipated! although it is a hassle, get a second bottle of mag citrate, & repeat the 1/2 bottle every 6 hours dosing. Drink water to lubricate your stool. You may also take 2 fleet's enemas & hold them in as long as you possibly can. Evacuate your bowels, and then walk around the block to stimulate your intestines. Last resort is to digitally cut stool into pieces to pass.