should i go to the doctor?

for the last few days i have been debilitatingly tired. literally sleeping all day and night except to use the bathroom and eat. I am also voraciously hungry. cant seem to get enough food. just low grade temps so far and a little constipation. i really don’t feel "sick" but these symptoms are very troubling. my first thought was Mono, but i had that in high school. could this just be a virus or should i go to the doctor? I cant get an appt for three days and if it is viral it will be a waste of money to go because they wont do anything. opinons please?
(i havent done anything out of the ordinary: eating, drinking, etc.)