Symptoms: nausea, fatigue, lower abdominal discomfort by c-section scar, & headaches. what could this be?

Many, many things.: Suspect the c-section is a red herring (what us docs call anything that has nothing to do with the diagnosis). The others would be called non-specific systemic symptoms, each of which could warrant a diagnostic work-up. It's probably a viral illness. So, do the usual: drink 6-8 glasses of clear fluids daily, get enough rest, take daily walks. If symptoms becomes severe, or persist for > 3weeks, c ur gp.

Wound infection?: This could be one of several things such as early infection, hernia, adhesions, bowel obstruction, etc. I would see your gynecologist or family physician for an evaluation and possible diagnostic imaging.