15 weeks and one day hiv test negative is it conclusive?

I'm worried, because I had a exposure high risk (umprotected)
in fact I did several tests during the three months
and all were negative.

The incident happened on july 8 2012

first hiv test type 1/2 in a laboratory at 6 week (negative)
second hiv test in other different laboratory on oct 22 2012

the difference of these two labs was, that the last one took me out two large tube of blood.
and also took two days to give me the result
it was also negative.

15 weeks hiv negative and im still worrie
do i have to test again?
do you think i am free of hiv?
can i have sex with my wife with not problem you know ,
should i trust 15 week hiv test negative? Tweet