How far below the ribs? have you ever had issues with candida? and how long after you eat do you notice this? also is it always after eating nuts? or any raw vegetation? Nuts are difficult to digest for some, they should be soaked before hand to remove some of the toxins, phytates and enzyme inhibitors.
If it is very much under your ribs I would say it is not your stomach but perhaps in the descending colon. Be aware as I noted before that for some whose digestive fire is not up to par, that digesting raw food is very difficult and many get bloated and do harm, the cellulose in raw food is very difficult to digest, It is my experience that this cellulose gets lodged in the colon and is not eliminated setting the a host for candida which thrives on this undigested cellulose. Most people have several pounds of this material in them at any time and a raw foodist with poor digestion will have much for for sheer abundance. If this is the case I recommend you take a digestive enzyme that is high in cellulase to break down these indigestible fibers that are not removed normally.