Hi there! Yes, I can absolutely relate to your story. As a 30+ years sufferer with IBS, mostly C, I have had many experiences like yours.
Three years ago I was dx was a fully impacted colon. Bear in mind that I was "going" at least once a day, albeit ridiculously small amounts (my kitty yields more waste) so I was shocked to learn that I was constipated. The GI doc told me that often, when one is so completely backed up, the small amounts that eek out here and there are actually squeezing around the more impacted matter. Even before he did the X-ray, he concluded just from the description of my symptoms that I was obviously impacted. He recommended a colon hydrotherapy clinic for a more "natural" clean out. Since I had been using laxatives all my life, he thought I might benefit from this alternative treatment.
Colon hydrotherapy is an intense and deep "enema" which reaches far into the intestines for maximum effect. When you begin to release the waste, it travels through a long hose and into a machine that has a window. You can see everything that is being eliminated. I can't tell how absolutely HORRIFIED I was by the massive amounts of "crap" that came out. I continued this treatment for four months, at least once a week. I never felt better in my life than during that time.
In my experience, those of us with chronic IBS C have a very hard time with fiber supplements. For me, they simply compound the problem. I do much better if I get my fiber through foods like winter squash, cooked greens, yams, lentils, moderate amounts of beans, fennel, and multi-grain pastas, among other things. I also make sure to use appropriate amounts of olive and flax oils in cooking and on my food. I find it helps get things moving. And, of course, WATER, WATER, WATER.
As for laxatives, I refuse to take Dulcolax or any of those other pill type stimulants. What you described, the nausea, the shaking, the color draining from your face, was my typical experience with these meds. Now, when I need to do a thorough clean out, I use Magnesium Citrate. It's really a wonder laxative. It does the trick quickly with absolutely no cramping or nausea or anything other than just the result I want.