First is explore any physical medical reasons for the nausea followed by lack of appetite. Be persistent.

Second is review your meds list w/ prescribers for any meds that have reduced appetite as a side effect. Consider the time line, and if they could play a role.

Third is address any stressors in your life that happened along the time of symptoms. Address this w the help of family, friends, and mental health workers as needed.

Fourth is consider the possibility of an eating disorder. Learn about them, and if this seems like you. Describe symptoms to your doctors and others health care workers for diagnosis.

I am sorry you are struggling.