It could be something other than the bath... what did you eat pror to that? Could it be that it got to yor bowel and upset it?
Have you tried using hot packs? If they help you, it's probably something other than the bath...
I don't know if baths can cause bloating... But when I take a bath, I get so nauseaus I think I will surely die and have to get someone (husband) to take me out of the bath right away (getting nauseaus is inevitable and very quick, so I don't take baths other than for medical reasons, when I need to get very warm quickly)
My stomach is totally messed up at that point and I would think my IBS would flare up (I haven't taken a bath since I got IBS so I can't know for sure).
However, I think I am a sort of extreme case and I think the nausea is caused by the hot water moving around and me not controling it. I get nauseaus in cars, trains, trams, planes, pools (if I am not swimming all the time) and the sea, so the bath is no exeption (the analogy is that things are moving around me while I am not moving my body), it just happens much more quickly and I do feel like I'm going to die.
I hope you feel better soon.