Low fever and headaches for almost a month

Hi,
For more than 3 weeks I have a low fever (98.9 - 99.7F / 37.1 - 37.6C)  with headaches in the forehead.
I did blood tests and everything came fine. Then my doctor sent me to the ER- they tested my eyes to see that there is no pressure inside the skull, I had a sinusitis test which came OK as well.
After few days I did a CT test in my head and the doctor find nothing wrong with it.

All the time I've been told that it could be some kind of a virus, but it last alrady for more than 3 weeks.
All of the paracetamol pills do not affect the headache nor the fever.

I'm waiting now for the results of infectious mononucleosis. In the last 10 days I feel very dizzy and weak.
If the mono results will come back OK - what should I do?
Can a virus with the above symptoms last for almost a month?
What are the next steps and tests I need to do in order to find the origin of the problem?

In the last 3 days I started to cough and the fever went to 100.4F / 38C - I took some codeine medicine which helped with the fever and the cough, but I still feel dizzy. The fever went down again to the low fever mentioned above, and does not come down more than that.

Please advise what do you think it might be and what should I do next?

Thanks,
Hila

[Dr Santos]

Hi Hila,
How are you? Were you able to have your fever and headache checked? A virus infection usually lasts for a few days only unlike that of bacterial infection which lasts for a longer period of time. However, there are some types that stay inside the body and become inactive. they get reactivated when you are exposed to triggers. Take care and hope to hear from you soon.