Had possible exposure with girl(s) in July-Aug 2007 (unprotected oral sex receptive and vaginal sex w/ condom). Had 5 HIV ELISA test since then. Last two where in Oct 10 and Nov 10. Since that time, I have had swollen lymph nodes in groin area, and now swollen lymph nodes in my neck which started in Mar, 2010. They say swollen but my HIV ELISA test (Oct and Now, 2010) where negative. All three test before those two dates where also negative. Is there a possiblity of my HIV ELISA test being false negative? Can I say I don't have HIV?