You need a Colon Cleanse first and foremost. If you get constipated doing the flush you are probably getting a backflush of waste which will make you quite ill... waste and toxins are just circulating around.
Things need to be moving downward efficiently. Thats part of the reason you aren;t getting stones out they can;t possibly be exiting the liver in this state and you'll end up getting stones stuck.
I would do a bottle of Oxypowder at least first, taken over a course of a week to 2 weeks or however long it takes for each nightly dose. Then do an enema or coffee enema the night before your flush.