I was looking up headaches on Google when I found your post and I think I know what could be going on with you, here are some options ...you mention working in a car dealership service department if not properly ventilated or if car exhaust could somehow be leaking into the building that your working in this could make you very ill and be dangerous.All car emissions produce a colorless,orderless poisonous/deadly gas called carbon monoxide,which can cause flu like symptoms including headaches among other neurological symptoms while not always deadly depending on how much and how long your exposure time is it can cause permanent lifelong damage and defects to organs such as your brain.I suggest you ask yourself this questionoes your headache go away or lessen when away from the dealership? Also buy a carbon monoxide detector at Wal-mart and put in building to see if you get a reading(keep in mind that you need to leave it in the buildfor carbon ing for a couple of work days) or have the fire department check the building monoxide,most will gladly come out and test,it's there job.Notify your employer about your concern.Also some hospitals or doctors can draw blood and do a Blood Gas Test for carbon monoxide,the only catch is that in order to be detected in the blood the blood must be draw right away after the exposure cause after you leave work and get into fresh air it leaves the blood pretty soon.look it up with wikipedia or google "carbon monoxide poisoning"



Or maybe your dehydrated or have dehydration headaches,heat exhaustion or heat stoke.