If your so worried maybe you should go get another test done just to make sure. Having a persistent headache can mean a variety of things, so you shouldnt think its only one thing, but have another test done just so your not worried about it anymore and you rule that option of what it is out.
It could be so many other things - a migraine, a sinus infection, anything! Make an appointment with your doctor and tell them about this.
honey please dont stress yourself out like this..... testing 2 years after exposure is fail proof. you are stressing yourself to headaches,,,,,, i know because i stressed so much about getting an hiv test that i got shingles! and when the test came back negative i was relieved. the risk, even if you had intercourse or shared a needle with an infected person is very very small(not to be taken lightly, but thats the comfort my doctor gave me when i was worried)