I tried Levsin once. I think the side effect that I didn't like was that it gave me heart palpitations and it scared me so I stopped I'm a big chicken when it comes to new medications. Maybe had I given it time the side effect would have went away? Who knows but I never gave it a chance. Librax made me feel the way you are feeling. It may go away though the longer you take it.
As far as the prep. I did the 3 8oz phospho soda stuff. Only could handle two of the 8oz glasses. I seriously did not need 3 as at the time I only weighed like 80 some lbs. Oh I was cleaned out for sure with only 2 glasses. I found that when I mixed it with Iced Tea or something it was even grosser. People say ginger ale or sprite works good. ALSO if you use a staw and put it toward the back of your throat you really don't taste the stuff. I ate all I could ALL day. I had made up little containers of jello (except the red dye jello's)had a million cups of chicken & beef broth, ate tons of gum and candies. (I'm sure my glucose level was sky high ) You'd be surprised how you won't feel that empty. I'm emitaphobic BIG TIME and yes I won't lie, I nearly gagged and threw up after the first glass. I ran to the toilet a few times but NEVER threw up. For some reason it stays in. God only knows why! IT's the weirdest thing. The procedure itself it the easiest. You won't feel or remember anything.