Symptoms: dizziness, fatigue/lethargy, headache upon standing, sensitive to light, high fever. Nothing else so far. Any ideas as to what it might be?

Dizziness, fatigue/lethargy, headache upon standing, sensitive to light, high fever. I would recommend that you go to see your primary care doctor about this issue, especially if the pain is persistent or worsening. There are several different potential causes of your headache, and your doctor can perform a thorough physical examination and help you figure out what might be going on. The fact that the pain is mostly on one side of the head would be most consistent with a migraine. Migraine, classically, is characterized by a pulsating pain that is localized to one side of the head. Chronic sinus congestion Other symptoms that often go along with migraine include nausea, dizziness, sensitivity to light, and changes in the vision (such as wavy lines or flashing lights). The pain could, however, be from other causes as well. For example, if you have Lymph nodes in one area, or in multiple areas chronic sinus congestion, that is mostly affected just the sinuses on the left side of your head, that could definitely cause an aching pain that was mostly localized on the left. Your doctor can help you figure out what is going on. Based on the likely cause of the headache (migraine, sinus congestion, or something else) they can also make recommendations about which medications would be best to treat the pain. Good luck!