Well, you seem to be reporting regular bm's due to psyllium as SFS and diet. Perhaps--and this is a whacky and wild thought--after your bm's you have a huge air pocket (i.e. an empty void after the SFS unloads whatever you put into yourself), giving you that famine belly/pregnant balloon look.
I know with me, asthma is a factor. I do swallow air!
Like you, my favourite breakfast is WATER/fluid. I can't think of food until later in the day without nausea and vomitting (I take some pow-wow am meds.).
Keep exploring. Some enzymes, though, with those gassy soy and fibrous cereals might help break down the lignans and the cellulose/hemicellulose. They really really are effective for me.