Hello, I suffer from IBS-C. I was told to do low FODMOPS too, but also told it’s a constipating diet. So I stick to no gluten, dairy, yeast, legumes, cuaciferous, and take note of what else bothers me and the rest of the list with a grain of salt as everybody is different. When my body isn’t slow jammed I do ok with phylum husk daily. That being said that’s not been since right after my first colonoscopy. Now if I take it, trying to make myself go, I end up distended and it makes things worse. I use a product called IBD Guard which is for both types of IBS to calm your gut to avoid flare ups. Fasting sometimes helps when things get bad, just to clear everything out and reset.

Yes! I have IBS-C and my GI recommended Benefiber. Made it much worse and gave me really bad cramps. Don’t take it!

I have not tried fiber supplements, and I've been attempting the fodmap diet for 2 months now. Yesterday I saw a naturopath doctor who thinks I have SIBO--small intestine bacteria overgrowth. My gastroenterologist has never mentioned this possibility. He put me on medication and seems stumped that I am not better.

There is a modified fodmap diet for SIBO and it eliminates white starches (rice, all potatoes, oats) plus a few other things I had still been eating.
For me, anyway, I think what I eat makes a world of difference. I had no starch with dinner last night and feel worlds better today.
You can Google SIBO diets to give it a try.

for me, any fibre make by ibs-d worse

Try a different type of fiber then.