I'm sorry you haven't been feeling well. It's good that you've got a doctor's appointment to get checked out.
This could be a number of things, from a low grade infection, to a virus that's lingering, to allergies, to an autoimmune disease such as lupus (one of my first symptoms of lupus and
one that continues to "tell" me when I'm having a flare is a lingering sore throat and
extreme fatigue with no other known cause)
During these times, do you run any fever? Any nausea/vomiting