Healthy male w/ Nausea for 14 days

I am a healthy 37 year old male w/ no history of any serious illness or stomach problems.  However, 14 days ago I woke up with severe nausea and burning in my stomach. Throughout that day the nausea got worse, a fever of 102 developed and I had horrible diareah. It was so bad I went to the ER, where I passed out (they said from dehydration). They put me on morphine and zofran and ran a bunch of blood tests. Within 4 hrs my pain level dropped from level 9 to level 3. The ER doctor diagnosed mr w/ gastroenteritis and sent mr home e w/ a zofran script. Next day I had most of the same symptoms + general feeling of being tired/lethargic. Day three I started to improve, except the nausea and burning has been persistent. On day 10 I saw a gastroenterologist, who examined me and concluded that I just have a bad case of gastroenteritis and nothing more. He said it will go away soon. Since I told him I felt like my symptoms were improving he did not write another script for zofran. The day after I saw him my nausea and stomach burning got worse even though I was still on zofran. Today (day 14), I'm out of Zofran and the nausea and burning is brutal.  All other symptoms are gone (although I may have diarea (diarrhea) masked by the Zofran, which seems to make mr constipated). So, my questions are (1) Does this really sound like gastroenteritis to you? Don't most of these cases last just a few days? Wouldn't it be extremely rare for such symptoms to last 14 days in an otherwise healthy 37 year old? (2) could it be something more serious, like stomach cancer? (3) should I go to the hospital or urgent care now or wait for my next appointment with my gastrroenterologist in 3 days. Note that today is Saturday.  Sorry for the long report and I appreciate you taking time to answer.

[CakeisgoodFrostingisbetter]

Just another name for stomach flu  
Viral gastroenteritis is an intestinal infection marked by watery diarrhea, abdominal cramps, nausea or vomiting, and sometimes fever.

The most common way to develop viral gastroenteritis — often called stomach flu — is through contact with an infected person or ingestion of contaminated food or water. If you're otherwise healthy, you'll likely recover without complications. But for infants, older adults and people with compromised immune systems, viral gastroenteritis can be deadly.

There's no effective treatment for viral gastroenteritis, so prevention is key. In addition to avoiding food and water that may be contaminated, thorough and frequent hand washing is your best defense.

read this info http://www.mayoclinic.com/health/viral-gastroenteritis/DS00085/DSECTION=symptoms