It is said that the worse the symptoms of detox on a fast............the greater the need for it.
You may find it easier in the transition to a water-only-fast, to live from a plant-based diet for a couple of weeks beforehand; this will help to reduce your levels of toxemia and make the W/F more enjoyable, whilst eventually avoiding the nausea.
You should of course only eat when hungry, and this could mean just one meal per day: any food eaten when not hungry, will only serve to ferment and putrefy this in your intestines, and adds to the burden of toxemia generally.