I Have Had Unusual Fatigue, A Long Lasting Persistent Headache

I have had unusual fatigue, a long lasting persistent headache (3 or more days), dizziness and I have had a feeling if being hot/overheated I am a 26 year old male. I own cats and I'm not allergic to them. I can eat but not a lot or I get a sensation of nausea. I am sexually active with my girlfriend and we do not have any STDs. I have a job that requires me to work outside (in Virginia) in various weather conditions. Is there a possible explanation for my symptoms?