Hi,
Welcome to the ehealthforum and I am glad to help you out.I am not sure whether you mean chronic nausea by sickness. If that is the case, then it can be due to stomach disorders such as gastroenteritis, liver/gall bladder disease, cancer, medications,inner ear diseases like labrynthitis, ulcers/gastritis, metabolic like diabetes,hypothyroidism and adrenal diseases or neurological causes.
I will sincerely advise you to consult a physician and get these possibilities ruled out one by one.Detailed and comprehensive lab and radiological testing is required to confirm a diagnosis.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care.