How long does it take and what should I expect?

Usually on the anxiety boards and ran across this just today. I'm a long time sufferer of IBS-constipation.  I am having surgery next Tuesday and need to get more regular or cleaned out some prior.  Dr. said to start using Miralax this past Monday.  Have mixed it with Carnation instant breakfast Monday, Tuesday and Wednesday mornings.  Am eating veggies and fruit all day.  Haven't noticed any change.  I decided to try a second smaller dose this evening (mixed in some hot tea).  Still nothing.  How long does it take for this to work?  Should I be putting it in something different to drink?  I've got until Monday to get this figured out.  This is worrying more than my upcoming hysterectomy surgery.  Any advice at all would be greatly appreciated.  My doctor has said no bowel prep is needed but just need to get things "moving".

I have had 4 abdominal surgeries with 3 different surgeons and all required a bowel prep before they'd go in. They said it was for my safety, an empty bowel lies flat and not much leaks out in case of an accidental nick.

One of our local gyn surgeons did not require his patients to do bowel preps. He can not longer practice in 3 of the 4 local hospitals and a woman I know will be getting millions from him because he perforated her bowel during surgery and since he hadn't required a bowel prep, she almost died. Her attorney proved that bowel preps before abdominal surgery were common practice.

I don't mean to scare you, I just worry when I hear a woman say her doc doesn't require a bowel prep before a hyst. You might want to do one anyway.