Thanks for your query, an elucidate history...
The cause of an non-stop nausea
can be a gastritis
, gastric ulcer, cancer or GERD or intestinal problems.
The other causes of any general disease which can produce the extreme fatigue
Third cause is related to the Psychogenic.
To get a proper diagnosis you need to undergo the following:
-General Check-up by a Physician to find out the signs and advise you the further investigations and to treat the cause.
-Investigations of the blood, urine
and X-ray chest.
-To get the symptomatic treatment
-Upper GI endoscopy
-Proper treatment as per the diagnosis, once you get it.
-Get an opinion of a Gastroenterologist too.