Call the on-call doc at the GI practice. They probably are very used to this question and have standard answewrs. They will ask have you taken everything on schedule, and the color/consistency of what you are "evacuating." They may tell you to come in early if you are unsure of how well the prep work. Anyways, I suggest calling them since they are the ones to make the final decision.
I had to talk to mine during my last prep because I couldn't keep the stuff down, and they helped me adjust the dosing schedule so that everything worked out fine.
Best of luck to you.
May 06 Stage IV CC: liver + ovarian mets
Oct 07 inoperable lung mets
Feb 08 - April 2012 chemo
allergic to oxaliplatin and irinotecan
Aug '12 - clinical trial
Sept '13 - trial over, nodules growing
staying on study drug until they kick me off