Dear Margot,
I hate to tell you this, and it probably isn't this, but nightsweats and nausea are indication that you are not matabolising sugars properly...in other words, this could be pre-diabetes or even diabetes.
The nightsweats and nausea are due to a condition called keto-acidosis (meaning your blood sugar is too high and your kidneys can't get the extra out of your blood)/. It makes you nauseaus as well as causing nightsweats.
Healthy adults (who are at a normal weight) can develop this condition due to a variety of problems that have nothing (or very little, anyway) to do with weight or diet. It may be an autoimmune issue or even a genetic "tick" that has a tendency to show up as an adult (rather than as a child).
If you know anyone with diabetes or prediabetes then ask to use their blood glucose monitor (you can share a monitor, just make sure you use a clean lancet device and that he/she records your check as a "test" on their monitor). Check your blood sugar 2 hours after eating a normal meal. If your blood sugar is near or over 140 then you are considered "high" and you should make an appt with your MD.
If it is over 200 two hours after eating, then I would go to an urgent care center because you might be in danger of developing ketoacidosis if your condition remains untreated. If you let this condition continue without treatment then your hospital stay will cost you thousands or even tens of thousands of dollars. If you catch it early, you will be referred to an endocrynologist and learn how to control your blood sugar--sans losing the tens of thousands of dollars! :)
There is no point in being afraid of testing this. It is better to control your condition then to let it get crazy bad. If you are diagnosed with Type 2 diabetes or prediabetes then you will likely only need to take oral medication to control it. Type 1 is almost always present in childhood, so if you are an adult, you likely don't have to worry about that issue.
Hi there!
Well, without a detailed clinical evaluation it would be difficult to determine the cause of your symptoms. Possibilities that may need to be considered include low blood sugar, GI infection/ inflammation, GI motility issues, stress/ anxiety, systemic infections/ inflammations, micronutrient deficiencies, hormonal/ endocrine abnormalities, medication side effect etc. I would suggest getting this evaluated by a primary care physician initially and depending on the cause diagnosed/ suspected, it can be managed accordingly or specialist care may be sought.
Hope this helps.
Take care!