I am experiencing fatigue, headache (occurred: 1 - 3 hours) (quality: dull or aching sensation) (time frame: gradual onset) (side: left, right) (severity: moderate) (better by: nsaids (ibuprofen, naproxen, etc.)), popping or snapping sound from knee joi

Need more info. I would need much more info to give a good answer. For example, has this been going on for days, weeks, months or years. Your symptoms are very nonspecific so can have multiple causes, from an acute virus to chronic infections like Lyme Disease to food allergies.
If this has only been a few days it may be a virus that will go away on its own. If more chronic I advise seeing a good Dr. to evaluate.