Stress and anxiety
have very complex effects on the body. For example, being chronically or acutely stressed out can lead to problems with sleep and appetite, fatigue, nausea, and many other symptoms! This all just illustrates how closely connected our minds and bodies are and what profound effects they can have on each other.
Regulating stress is very important. You can try to do this, at least at first, by trying to eat healthy, balanced meals regularly and making sure to get some exercise every day. This will go a long way toward making you feel better. Avoiding caffeine and alcohol is also very helpful. Finally, trying to establish a good sleep rhythm where you go to bed at about the same time every night and get 6-7 hours of good sleep can help.
At the same time, especially if these stress reducing measures do not work, you have to consider other potential causes of your nausea. For example, acid reflux
disease, inflammation of the stomach lining (gastritis) and stomach ulcers can also produce nausea and a "weird sensation" in the stomach. If the symptoms persist you will want to go see your primary care doctor
to see what else might be going on.