I read through your sig and I think, damn. But I too am amazed by how you have been fighting HER2 for so long and are still winning. I'm sorry it hasn't gone away but look at how amazing you are. You can feel weak and low but count me amongst your fans and let me give you virtual hugs and tissues when you are feeling low.
Let's talk about your gut though, have you ever heard of such a thing as resistant starch? It is a type of carbohydrate that your body doesn't digest but the beneficial flora in your gut can digest it and it is totally good for you. What is even more crazy is that it costs pennies and yet docs don't know about it.
The thing is that it can totally help with diarrhea, something that many suffer with during chemo. Supplementing with a probiotic and probiotic foods is important as well since chemo messes with your microbiota in ways that are 1000 times worse than antibiotics.
I'll post more separately about resistant starch but here are a few easy options:
1 tsp potato starch mixed with cold water
--or--
1/2 cup potato or pasta salad (must be cold, however you like it)
-- or--
1/2 cold boiled potato
Potential beneficial effects of butyrate in intestinal and extraintestinal diseases
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3070119/