The causes of feeling sick are iatrogenic (doctor induced like medicines), toxic, or infectious causes; gastrointestinal disorders; and central nervous system or psychiatric conditions. Following are the main causes;
A. Central nervous system
2) Space occupying lesion in brain (Mass lesion)
4) Ménière's disease
5) Pseudotumor cerebri
B. Gastrointestinal symptoms;
2) Irritable bowel syndrome
3) Non ulcer dyspepsia
4) Peptic ulcer disease
5) Cholecystitis/cholangitis (gall bladder problems)
6) Hepatitis (liver inflammation)
1) Thyroid disorders
3) Adrenal disorders
D. Psychiatry disorders
3) Conversion disorders
So you need investigations like blood work again and hormonal evaluation (for bleeding; thyroid function tests, adrenal function test, prolactin, FSH, LH estradiol etc) with upper gastrointestinal endoscopy, blood and urine culture.
These should be able to conclude the cause.
Please feel free for your follow up questions.
I would be happy to assist you further, if you need any more information.
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