The bottom line is that you needn't be anxious any longer -- indeed could have put it aside after your first test. Your test at 45 days proved conclusive you did not acquire HIV last August. The next three were unnecessary but confirmed the initial result.

The HIV antigen-antibody (AgAb) tests -- also called "combo" and "4th generation" HIV tests -- are among the most accurate diagnostic tests ever developed, for any medical condition. They almost always are positive with 4 weeks of catching HIV (~98% reliable); on rare occasions they require up to 45 days, which perhaps you learned before your first test, maybe explaining why you chose that particular time to test.

You say nothing about the nature of your exposure. It makes no difference in understanding your test results; they are conclusive no matter how high the risk of HIV at the time. But feel free to let me know about it if you would like that perspective on your situation. In the meantime, congratulations on your negative test results. Let me know if anything isn't clear.

HHH, MD