Hello sir, I did a sex with a prostitute 6.5 months before. After this incident I had been experiencing almost all hiv symptoms. During this time I have tested elisa ab/ag test for 6 times (1.5,3,4,5,6, months respectively. All are negative. I also tested vdrl+tpha after 6 months. both are found negative. The problem I have severe headache now. Sir is there any chance to turn hiv positive after few months later, still now negative and is there any possibility the virus exist my blood but can not detect from the test as I had taken some antibiotics +pain killer medicine during this time? please do suggest me.