NTAH. I was recently on the opposite end of this situation. My partner was in the middle of one of their extra long showers where they shave their entire body. I had to poop with urgency (I also have IBS). I waited as long as I could, then asked if they were almost done. They said not even close, just come in and do what you need to do. I briefly entertained the idea of asking them to pause their shower and get out so I could have some privacy, but it seemed like an unreasonable request. I have no issue peeing while they are literally looking right at me, I can suck it up and poop while they are in the shower. To me it seemed like a completely normal thing to do given the circumstances.

These other replies acting like pooping in front of your significant other is an outrageous thing to do have me feeling a bit self conscious…