This is my favorite prep using Miralax. You can follow it up with any kind of liquid including vitamin water so you don't have to drink a bunch of sweet or disgusting tasting prep. I like it better then the Supraprep:
This is my #2 favorite prep: http://www.prepopik.com/about
Sadly, I've had enough colonoscopies that I am able to rate the preps
Ask your doc if you can do one of those instead. It might help prevent the headache. I am caffeine addicted so I think I get headaches from that with colonoscopies.
Good luck with everything.