Uny and others may disagree with me... however I had the same experience as you 5 years ago with bowel cleansers.
If you are drinking that much water, and it is distilled, or R\O, you could also be messing with your electrolyte balance... try a very small pinch of "whole" salt in all of your water... not enough to taste the salt - but enough to "sweeten" it... I actually prefer the Celtic Salt for this because of its mineral profile... less sodium.
You can also squeeze a bit of lemon in the water... this is like Gatorade without the Sugar and chemicals, and a real pick me up for many.
Barring that, my advise would be to try an oxygen based cleanser like homozone, colosan, Oxypowder , etc.
Get one bottle from a local HFS to try... if it works better for you, you will most likely find cheaper prices on line.
The less expensive ones like colosan (at least it was back then), works just as well as any other if you add drinking half a juiced lemon or some ACV after you drink the powder\pills down.
If things work out for you with this, you are one, that may need to go a different route with your Colon Cleanse as I was.
I remember blood typing back then too and Os were more like this (having better luck with oxygen cleansers) than others if I recall correctly. I wonder if anyone has done work with metabolic typing with this?
We are all different... and there is no "1" best method for everyone... there will always be a small percentage (most say in the range of 20% give or take) of people that will need to make changes or major adjustments to any one size fits all protocol...
Actually everyone is different and minor and moderate adjustments need to be made for most. Do not be afraid to follow your instincts on this one... empower yourself.
BTW - I do not Colon Cleanse per se, at all anymore and have 3 - 4 movements everyday.
If I feel my regularity is slowing down or drying out a bit, I exercise a bit more, drink a bit more fluids, eat more green vegetables, especially leafy greens, and\or put a pinch of Epsom Salt in nearly every glass of water I drink till things get moving at a comfortable pace again depending on my location and what I am doing - I always carry Epsom Salts with me when traveling... NOTE: you do NOT want to use so much that you get the scoots when you are not in a cleansing mode... just enough to act as a very mild stool softener.
AND with the oxygen cleansers, you may want to pay close attention to your mineral salts by continuing to eat mineral rich foods and such... perhaps a touch of whole salt when\if needed.
Pay "daily" attention to detailed body response to every thing you put into your body, including meals and drink. As you have apparently been doing with your account of your response to what you are doing currently.
Do not get discouraged because your needs may be different... empower yourself to find out what they are, and make the adjustments gently and accordingly.