Hello,
What you are having is chronic nausea and it can be due to stomach disorders such as gastroenteritis irritable bowel syndrome, liver/gall bladder disease, medications, inner ear diseases like labrynthitis, ulcers/gastritis, metabolic like diabetes, hypothyroidism and adrenal diseases or neurological causes. Cyclic vomiting syndrome is also stated to cause constant nausea.
I will sincerely advise you to consult a physician and get these possibilities ruled out one by one. You can take antacids or PPI blockers like omeprazole after consulting your doctor. Take an OTC lactobacillus preparation and yoghurt with your meals. Drink plenty of fluids and eat dinner about two hours before sleeping. Elevate the head end of the bed. Keep a food diary and note down what aggravates your symptoms and avoid them. Ensure to maintain optimum weight by regular exercise.
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 and please do keep me posted on how you are doing.