I do suffer from IBS, though the symptoms you mention are very rare for me.
I HAVE noticed my bowel function changing and getting slower on HRT. I'm not sure whether it has to do with changes in the muscle tone of my intestinal muscles or the fact that Spiro dries my system out.
I've gone to several different GI folks for my IBS. None of them did any good. One of them gave me about 28 pages of possible treatments involving various dietary, probiotic, and fiber supplement therapies, and told me to try each one until I found one that works. Another gave me muscle relaxants (which did nothing).
So I'm not issuing a ringing endorsement of going the medical route on this one. I don't think they really know much about this. Best thing I ended up doing for myself is cutting out junk food, eating fruit instead of fruit juice, getting lots of whole grains and fruits and vegetables and staying away from cheese and fatty meats.
Don't know if this helps, but it's all I know.