That's odd. Spinach is probably my safest form of IF. I puree it. I generally combine it with another SF veggie, i.e. mushrooms or beets or carrots or spaghetti squash or zucchini, or avocado, etc. I can easily eat 2 cups in a sitting without a problem (D or C). I even eat it for breakfast.
I promise I'm not pop-eyed.
I do find it ultra gentle, however, if there is another high SF veggie (or fruit) involved. It's one of the few veggies that don't even potentially bother me enough to take Beano for, oddly enough.
Perhaps, try infusing smaller doses if IF throughout the day, versus hitting your system with a high-test dose, i.e. 2 c. spinach--especially if you are hyper-sensitive to spinach, lately. Also, sometimes we get in an undesirable IBS-status stasis when we do not vary our menus enough. It doesn't have to amount to much variety, please not. Maybe try some different grains and alternative snacks, including safely prepared fruits/veggies.