Hello - thanks for asking your question.
Gall bladder and pancreatic diseases are possibilities. These can be evaluated with an ultrasound and CT scan respectively.
Other considerations would be dyspepsia (either an ulcer or gastritis) - this can be evaluated by a repeat endoscopy. Splenic disease is less likely, but still possible. A CT scan would further evaluate this.
Nausea and abdominal pain are characteristic of delayed gastric emptying (i.e. the large-slow stomach). Typically, this is diagnosed in conjunction with diabetes or other neurological disorders. You can obtain a gastric emptying scan to evaluate for this.
If every test described above is negative, then musculoskeletal or rheumatological causes may be considered. You may want to consider further evaluation by a rheumatologist.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
gallbladder is a possibility. People with gallstones also are at risk for pancreatitis: it's easy to check those things out. Hernias of the abdominal wall are usually in the midline and fairly easy to diagnose as a lump, sometimes an intermittant one. There's not much a spleen would do to cause intermittant symptoms for 10 years.