I am not a doctor and cannot address your symptoms from that standpoint.  However, I have a lifetime of experience.  Have you had your inner ear checked out?  The nausea could very well be in your head and I do not mean psychologically.  I have been through countless neurologists and ENTs.  I would highly suggest you be examined by an otoneurologist, an ear doctor who specializes in inner ear disorders.  When I take decongestants (pseudophedrine, not the OTC replacement) my nausea disappears.  Also, diuretics are helpful.  For me, this is because I have too much fluid in my inner ear.  There are many causes of inner ear problems.   An accurate diagnosis for me also led to allergy testing.  Have you been tested for food allergies?  I have environmental allergies, but turns out food allergies are my worst offenders and the worst contributor towards my ear fluid.  So, don't stop with just the environmental allergy testing.  I spent over 10 years looking for answers and doctors (not to mention thousands upon thousands of dollars) who could handle it, so I know the frustration you must feel.   Be persistent, and good luck!