I'm not quite sure what you mean by cramp in the ear, but I certainly get pain in my ear, usually my right ear with my IBS. I have a theory that after 35 years of IBS, I now have fibromaylgia and TMJ. Trying to get an answer seems impossible though!
It could be that you are straining to go to the toilet. I have IBS D and sometimes when I have stomach cramps I get a headache because I hold I breath. I try and relax but it is not easy .
Have you considered TMJD as a possible explanation? I think my IBS was caused by TMJD; my IBS is largely better now but I think the TMJD (which isn't cleared up yet) is still giving me a tendency to constipation. It also affects around my ears although I wouldn't have described what I get as cramping - it's more like pressure and ringing sounds, and possibly might explain why I'm a little hard of hearing or maybe that's coincidental. To investigate you could consider looking for information about TMJD (also known as TMJ and temporomandibular joint disorder) online; you could also try lying down and relaxing, gently working the muscles in your jaw, and observing closely the sensations in your head and jaw area to see whether it is helping or not.
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