How much Miralax should I take to "clean" myself out? I'm severely constipated & the regular dose isn't working.

Try enema. If laxative has not worked, you may try Fleet's enema. The medication is available over the counter at drug stores. Drink enough water so that your urine is mostly colorless and increase your intake of fiber by taking Metamucil or fiber foods. Consult this site for fiber foods.