IBS. Sounds like IBS and internal mycoplasma issues, possibly with other pathogens as well.
I have some interesting info for you:
My 3rd child was born with thrush (candida) in her mouth so bad she could not eat without crying. She also had the extreme red constant rash caused by the bowel movement that I would immediately clean off and air out her bum in the sun, do the ointment, just like you are doing, etc. It would get a little better (until the next poo). It was a constant battle. She also had a distended belly. All these symptoms bothered me, but the pedi blew them off.I guess they see it so much they call it normal now, or something, because I had already had two children and neither of them had these issues, especially not a big bloated belly.)
She was treated w /Nystatin, an anti fungal for her mouth, only until the rash in the mouth was clear. I could not get the pedi to aknowledge she also had the yeast internally or that her bum rash correlated to the fungal issue in her mouth. As she grew, I noted failure to babble like my other two, 2 months later than my other two to sit up ,roll over,or walk, didn't cruise furniture, didn't hold her bottle, etc.. which they also blew off. When she would get sick, she would stay sick for a long time, and ear infections were a constant issue for a while. When she was boostered at 5 months she got a cold the next day and that's when the ear infection(s) started . I look back now and I see she had toxic overload to the max.
Fast forward 6 years. She did end up having some verbal communication issues, a mild form of autism. This child still has bowel issues, (soft poo and diarrhea, cramping pain, etc)... and the red rashes come and go (rashes to a lesser degree) around her bum and vaginal area. She has IBS. We've always thought she didn't wipe good enough and got her baby wipes for the bathroom, but I was doing some online poking around on a childhood rash site and found a picture of a rash around a child's sex organs/bum that looked very similar to the rash she gets on and off.The inside area of the rash is clear and there is a red line around the outside of the rash, like an outline. It said it was caused by strep bacteria.
For years I have been convinced that she had internal candida and all these issues were from the candida source. Not being able to get meds from a doctor, I started herbal meds. Caprylic acid and garlic to name a few. More and more research has brought me to new insight. I found data to support that everything she has been going through is traceable to once source, cell wall deficient bacteria, or, mycoplasma. A tiny bacteria that can bud and striate (like fungus) That can be passed from mother to child , and is prevalent in society. It suppresses the immune system so much that viruses, fungi and co-bacteria thrive, hence, all the symptoms. They named it th1 disease. I have been dosing her with herbal SAMENTO which has helped some, (I noticed her voice less gruff and she pays more attention, less aggrivated outbursts) but I am off to the doctor's today to push for a QRIB-b test.
Here's a link. read it through, you'll note IBS is on there: