If i have flu i usually wont go to the doctor because i have my own stash of meds at home :) If you dont have medicine, pls go to the doctor to get it. It wont get better if you are not eating medicine.
Do you mean a cold or a flu (influenza)? If influenza, best to go see the doctor. But either way, if it’s been going on since Sunday, good to get a doctor check on it