Yes, I have a similar problem. I have no proof it's connected with IBS, but body systems are all part of the same organism, so maybe.
I do have some marked misalignment of the pelvic area (one hip bone sticks out with a pronounced 'waist', and the other is straight up and down), I think some spinal scoliosis as a result, one leg is at least 1" longer than the other amd I have had lower back pain on and off for many years.
So...going back to the beginning of my IBS woes which started definitely early March 2020, but which I'd had some episodes of before that date, my lower back started playing up badly around those times. I get lower back ache before bowel movement in the morning. It can be so bad, I am desperate to sit on my "squatty-potty" toilet! Because when in that position my back pain is relieved instantly. After a bm, my back is easier.
Sometimes when moving about, standing to wash dishes, or walking, especially in the first few hours of the day, I get a pain that travels to my groin and upper thigh. Then there is numbness. My only remedy for it is to squat down for a moment, or to get onto the ground or floor. Then when I stand up again there's a sensation like ice cold sparkling water in there, and the numbness disappears. The feeling travels to maybe about 6" down the front of my thigh.
After that drama, things are usually better for the rest of the day, though my lower back aches again if I get tired out doing too much physical work.
I am sure there could be some connection with my IBS.
I haven't had enough medical attention for it, which is partly my own fault. I am not complaining.