Fever? Cold?

I seem to have a minor bug of some sort, consisting mainly of fever, variable headache, fatigue, and minor sinus problems. It's rather annoying, since it's mild enough that when I'm resting, I pretty much feel fine, and want to get up and do stuff. Yesterday, for instance, I dug a bucket of dandelions and my body is complaining about it today. I think I may go for a short hike today anyway, since cool air seems to help (so does cold water). Preferably someplace flat so that I don't overdo things. *sighs*