September 15th I was sexually involved with a friend (With protection) But I might have a blister on the inside of my lower lip while performing oral sex. 1-2 weeks later I developed cold,cough & head ache. That was treated with normal OTC medication. I then decided to get tested for HIV(AB duo) VDRL HEP B and C. My first test was on 3rd October, 2nd on 3rd December and recent one on 26th December. All were negative. But I am still worried that I might have contracted HIV disease. My questions are Were the cough, cold and headache simply coincidental ? Is it possible to contract HIV if I had an ulcer while oral sex ? How accurate is the AB duo test and should I trust my negative result as conclusive ?