It's definitely the combo and concentration. I can't give the specific science, but I there are nutrient inhibitors in many greens. Too, it could be due to a very high concentration of minerals. Many greens are high in Iron, which we don't need too much and is easy to over do for a organic veggie lover in america. So on its own, taking in 450% of your daily requirement of Iron through juice may be ok- because that is all the digestive system is putting energy towards, but when you have a variety of others things in there the digestive system is producing enzymes and other stuff for the proteins, fats, carbohydrates. I do remember reading something about fermentation in the gut when combining juice with solids. They say the same thing about mixing fruit with regular meals.
Even though some people may be totally cool with downing a potent juice with a meal, it seems at this point in your life it's not wise.
We all function somewhat differently.
Dr. Mercola has a intro to juicing on his website which is pretty informative.
Some people will mix fats like coconut, flax, hemp, or coconut milk with their juices.
When we mix fat with things the nutrients become more bio-available.
Also, I'm no juicing expert. Though, wheat grass juice is incredible for me.
I use it almost daily as a part of balancing blood sugar issues. - and it has many other incredible benefits.
Any other questions I may help you with? Did I address your questions well?
Don't be afraid to admit you want greens.
Imagine how your creator would react if you yelled, "lord I do not want your greens. They're just kind of here."
Also, it seems large quantities of probiotics for a few months may serve you well. I recommend "Primal defense ultra." above all other probiotics.
That may actually address the issue. Last year I could see myself with the same issue you are experiencing, but now I can mix juices with other stuff with no problem. I also had an intollerance to gluten among many things, and now I have no digestive issues (besides blood sugar) due to that particular probiotic. No other brand was effective- when I started with that things changed dramatically.