Hmm, had a small section of chocolate (not even a full "square" on the bar of Green & Black's 85%) and had a very quick digestive response. Not a pleasant one either. Googling tells me that this is common with IBS (chocolate intolerance in particular).
So I think that means I have IBS-C (for constipation). IBS is kind of a general term for f'ed up bowels, as far as I understand. I'd like an official diagnosis for peace of mind. I guess that's a remnant in me that is still looking for answers from doctors.
I may try Miralax (after I give the colostrum a good run), as I've heard from multiple sources, including people here, that it's okay to use longer term. It's just another thing to try so I can definitively say "I've tried it". Googling "colostrum ibs-c" comes up with some positive results, so maybe I'll get lucky.
I'm just keeping my fingers crossed it's not a FODMAPS thing and just an unfortunate long-lived symptom of being too low carb (for my needs) for too long.