abdominal pressure & nausea

I am a very healthy 50 year old that usually can take pretty good care of myself without having to see a doctor, but I have a problem that I can't diagnose myself and know that it is so broad that I will end up going through invasive tests and probably perscription drugs to only treat the symptoms. Maybe you can tell me what you think might be the problem.
For several months I have had a bloated stomach feeling after I eat. It doesn't go down into the bowel, only the stomach area. The next phase seemed to be a slight crampy belly feeling after eating. In the last week, it has gotten much worse, more pressure, more nausea, more cramping and pain, sometimes the discomfort extends down into the intestines and I am having occasional diarhea and sometimes an urgency to go, but not much happens. Right now, if it wasn't for the months of build up to this,I would think that I have a viral or bacterial episode going on. My stomach is strong in most respects. I can take ibuprophen on an empty stomach, or coffee or water and I feel fine, but when I put volume in there the discomfort starts.
I've read quite a bit, but I can't seem to find anything that describes my symptoms very well. Do you have ideas? Thanks Tweet