Another cold question - brain chemistry

Why is that, when I have a common cold (or more recently what seems like a months long cold-like malady without much nasal congestion) I fell sleepy almost all the time? Sometimes I literally can’t keep my eyes open. Even if I’m at home and am able to sleep its seldom for more than 20 minutes and I don’t wake up refreshed. What is actually going on at the brain chemistry level? Serotonin? Melatonin? Something else? Why does my body think it needs sleep when I already had my normal eight hours or so. There’s only so much coffee I can drink and even that doesn’t work well. A good cardio workout tends to wake me up for at least a little while but going to the gym when I REALLY feel like sleeping takes alot of willpower. What gives?

I wish I knew the answer to that. I too have had something like this off and on for the past 3 yrs. I assume it’s a cold because there are coughing spells now and then and a sneeze or two, but there is no wetness or congestion. Just an overwhelming tiredness. Sometimes I feel ok for a day or two and then it’s back for a week.

Guess the medical profession hasn’t heard of it yet or had the time to figure out what it is.