A couple of weeks ago, I started feeling extremely bloated after eating just a small amount. To describe the feeling, it was as if I had swallowed a large rock that was just lying in my stomach. Not so much pain as just an abnormal amount of pressure. I also have had a lot of nausea sometimes to the point that I have to throw up.

It almost seems that my stomach AND colon are involved in all this because I have heartburn a lot as well as difficulty swallowing sometimes and sometimes constipation interspersed with bouts of diarrhea. I've also been noticing a sharp pain that occurs infrequently just to the right of my navel. I do smoke (restarted after being off of them a year) and I drink a lot of Diet Pepsi. Also, I have taken a lot (up to 12 tablets a day) of Ibuprofen in recent months because of joint problems. I had my gallbladder removed in 1987, so I know my problems are not my gallbladder. Any ideas???

You could have gastritis, an ulcer or gastroparesis. All the symptoms you mention are similar to those digestive disorders. I have gastritis and I get the full feeling after only a few bites...I describe it as "a brick in the stomach". And you mentioned that you take alot of Ibuprofen--that can sometimes be the cause of ulcers.
Gastroparesis is delayed/slow digestion, which can give the feeling of food just "sitting" in the stomach, nausea and sometimes vomiting.
I'm not a dr. but those are the ones that came to mind when you mentioned your symptoms.

Donna