Nausea, UC and GERD

I am in my late 50's. I was diagnosed with severe ulcerative colitis in 2004, and when my anemia did not clear up after 6 months of prednisone and other meds, another colonoscopy was performed and the colitis was completely cleared up, revealing a tumor in the hepatic flexure of the colon.  This turned out to be stage 3C colon cancer. While Hurricane Katrina was pummelling New Orleans,  I had a partial colectome and underwent 6 months of FOLFOX 6 chemo, concurrent with 12 months of Avastin as part of a study.  I am cancer free today, (a lucky guy!) but not colitis free.  Making things interesting, I am also a diabetic, recently put on insulin.  Prior to that, I had tried Byetta for the diabetes, which created a lot of nausea, with occasional dry heaves.  It has been a year since then, but I am still experiencing nausea on a daily basis most of the time.  It is quick--comes on fast, and passes quickly.  It often happens in the morning and food helps a bit. Any time I am hungry, I am vulnerable.  But, it can happen almost any time.  Sometimes It results in dry heaves (usually only when my stomach is empty), but passes quickly.  It can leave me feeling lousy for much of the day.  I probably experience nausea or the feeling just ahead of nausea 3 or 4 times a day.  I also have GERD, though I do not usually experience heartburn.  I have some habits that exacerbate this, like eating late, as I get home late from work.  My colitis symptoms are also active but comparatively mild--a little diarrhea, loose stools almost always, 2-3 movements a day, mild cramping occasionally and a little mucus most times.  Bottom line, my gut never seems to feel very good, but this nausea thing drives me nuts.  Is autonomic neuropathy possibly at work?  GERD? Is it the colitis?  Or could it be all three?  Thanks for your help.