Hi welcome to health care magic...
Here your husband having fever , nausea and 
frequent urination complaint ..
So acute infective etiology like 
prostatitis , 
cystitis like UTI cause has to be searched for ....
You need to investigate with ....
1.CRP
2.Tempreture recording regularly with thermometer 
3.USG abdomen 
4.If needed per rectal 
prostate palpation
5.Urine routine microscopic examination and culture 
You need to given full course of antibiotic for infection...
First empirical antibiotic and than switch over according to culture report ...
Avoid excess spicy foods .
More water taken with fruit juice more. 
For vomiting 
domperidone or ondensetrone strip can be used 
Advise ; consult physician and according to cause specific treatment guided ...
Take care