If you have had a headache for 2 days along with the flu, despite taking a cold and sinus medication, it is important to stay hydrated and drink plenty of water. You can try combining two pain relievers like Tylenol and Advil, but make sure to check with a pharmacist first to avoid overdosing. Symptoms like these can last up to 7 to 10 days, but the fever should start to go down within the next 72 hours. If your symptoms worsen or do not improve, it may be necessary to consult a doctor.