I did the poop/vomit scenario a lot this year during a very bad flare. Every time I pooped for a good 3-4 weeks. I'd just started on an Iron supplement and my BM's had become much ROUGHER than normal. My BM's were also waking me up in the middle of the night.
But whether it was in the middle of the night or middle of the day that a BM came along, the flare got so bad that I began throwing up while I was pooping. AWFUL! I never felt nauseous until I starting the poop...to me it almost felt like the BM was somehow connected to the top of my stomach! Which of course, makes NO sense. But somehow the BM was causing a physical reaction in my stomach and I'd throw up the last thing I ate. Actually, I knew when I was getting ready to throw up...my body would start to shake, get chills and my mouth would fill with saliva. But once I threw up, I always felt FINE (with the exception of just being tired from the BM/vomit ordeal).
I was VERY anxious during this period of time...it's ONE thing having to deal with the awful BM's of Crohn's but to THEN have to deal with vomit??? If I'm at home, no big deal. Trash can is right there. But at work???? YIKES. The good Lord watched over me and I never had the vomit at work. But I worry about it every time I have to poop at work because the vomit thing comes on so suddenly! There's no "warning" - no nausea feeling. And there are NO trash cans in the bathrooms at my work. If I throw up there, it HAS to go on the floor...
When I FINALLY got an appointment with my GI, there was no explanation of the BM/vomit connection EXCEPT to say that it was all a part of the flare. They put me on Flagyl and Prednisone...a week later there were no more vomitting spells. I had a SBFT test and there were no problems. I don't have narrowing or strictures. I was worried that I had a blockage and that was what was causing the vommiting. Didn't have that either. The BM's were just so rough, they were causinig a reaction all the way in my stomach.
Its very exhausting dealing with that. I would definitely talk to your GI, though, to find out his thoughts on it.