I'm hoping an expert might be able to help me out, or someone who knows a lot about herpes testing. 

In February 2007, I began seeing someone monogamously.  I had recieved a full STD screen before this, and tested negative for everything, including herpes.  In April 2007, I slept with the person I was seeing.  I trusted him, but just to be sure he hadn't unknowingly given me anything, I got tested in May 2007, and I tested positive for herpes exposure. 

My question, then, is how is this possible?  I thought that herpes II would take 2-3 months to show up on a test--but I got tested roughly four weeks later.  However, we had engaged in oral sex in April and early May--is it likely, then, that this is herpes I?  Just recently I have developed blistering sores on my genitals and my doctor also believes it is herpes.  I know that the type of herpes is not exactly the most important concern I should have, but I have heard that type I is easier to live with in the genitals, so I was curious to know if this is true, and if I have thought through this correctly. 

(Also, before this man, I had not had sex with someone for three months, so I believe the negative herpes test before this relationship to be a reliable negative.)