Depends. A fever greater than 100.4f is the cut-off for qualifying fevers. If you have had one longer than 3 days and have symptoms such as pain, difficulty breathing, vomiting, diarrhea etc it is a good idea to see a doctor. You might consider going to an urgent care or your primary care doctor before heading to the emergency room.
Depends- call ur doc. Fever is due to multitude of reasons - viral/bacterial/fungal etc...Did you try tylenol/advil/ how old are you ? How long has it been there? Have any trouble breathing?Stiff neck? Constipated? Muscle aching? Etc...If you still don't feel comfortable managing it, call your doc. Most have phone availability 24/7.