I would definitely recommend going back to your doctor
for another evaluation. It is true that exhaustion, headaches, and swollen glands can be symptoms of a viral condition, especially of mononucleosis (or "mono"). These symptoms can sometimes go on for quite a while.
However, whenever there is a combination of swollen glands, exhaustion, and night sweats, it is important to rule out other serious medical conditions. In particular, it is important to rule out a lymphoma, which is a type of blood cancer which can often present with these symptoms. Ruling out a lymphoma is something that can often be done with a series of basic blood tests. However, many times, it may be necessary to obtain a biopsy
from one of the lymph nodes (swollen glands), depending on how large they are and for how long they have been present.
Your primary care doctor
can perform a full examination and help you decide what testing is necessary right now. If they decide a biopsy of a lymph node is necessary, they can also help you set that up. They may also decide to do some testing for some of the viruses that cause mono symptoms, as a positive test there would also help to confirm a diagnosis.