Been there. found the problem. I just couldnt handle casein protein. Are you using casein?
I thought this was worth highlighting, as I sort of found the same. I say sort of, because I think the typical high calcium content of casein was a factor in my version of that nightmare. During digestion, casein forms these clumps that eventually assemble further down the tract. So, these will link and bulk up. That's one thing; the calcium, for me, basically solidifies it, making it brutal.
I was taking a micellar casein, whose single serving of 24g protein included 75% of the RDA of calcium. I was taking two scoops! Not to mention, for a time, I was eating a good bit of mozzarella cheese in parallel! That's the kind of ****, pun intended, I want to wish on my worst enemies!
Since finding TruSciences Caseinator, which is a milk protein isolate and contains only 32% RDA calcium per scoop, I've had an easier time so far. And, I've also been consciously taking more magnesium to help offset some of this.
To the OP: Glad that you got checked, and I sympathize with your plight. I know you have been given direction to take something, so it's probably not worth fooling with... but for me, I know a few cups of milk, high dose magnesium, or 4 tbsp of MCT oil will get things "running" if I need relief. Of course, as others have pointed out, replenish with fluids.