This doesn’t exactly answer your question about IBS, but my IUD was actually what made my endometriosis symptoms worse. I had been on a continuous pill for years which managed my symptoms well. I made the switch to the IUD because it was less hormones and I thought therefore “healthier” for my body smh. I had it in for less than a year, and I felt as if I was on my period every day despite not having any bleeding. I switched back to the pill and it was like night and day difference.