Feeling off: dizziness, brain fog, fatigue, and a lingering cough... help?

For about five days now, I’ve been dealing with occasional bouts of dizziness, poor concentration, fatigue, and this overwhelming sense of lethargy—even though I haven't been doing anything more strenuous than resting. I’ve already seen my doctor, who told me to get some blood work done before following up with him.
I had a similar episode last year. Back then, I went straight to the ER, underwent a battery of tests, and everything came back perfectly normal; after about two weeks, the symptoms just cleared up on their own.
Separately, I’ve been struggling with a persistent cough for the past few months. I’ve gone through various diagnostic tests and am currently waiting on the results. My pulmonologist mentioned that since my lung scans look clear, he suspects the issue might actually be stemming from my sinuses.
Could those sinus issues be the culprit behind the lightheadedness and the other symptoms I mentioned? And what’s the best way to proceed? Should I push forward with the blood work now, or would it make more sense to wait for the respiratory results, assuming they might be linked?
Thanks in advance.

Look, I’m no doctor, so take this with a grain of salt. This is just my own experience, and yours might be completely different. 🙂

I dealt with cysts in both of my sinuses—they were totally blocked up. It left me feeling exhausted, and I’d get these dizzy spells or killer headaches out of nowhere. Eventually, those cysts started putting on a lot of pressure. My doctor steered me away from doing a puncture (not sure why, honestly) and instead had me go through various drainage procedures and other treatments. The thing is, if your sinuses are plugged up and you can't breathe through your nose—if that's even what's happening with you—you end up breathing through your mouth constantly. That just leaves you feeling winded and wiped out.
It’s definitely possible your sinuses are the culprit, but if I were in your shoes, I'd just run whatever tests your doctor suggests. It’s not like it hurts to know... and it might actually help. 🙂