Hi.. Welcome to healthcaremagic community forum..
Temperature of upto 99 degree F(37.5 deg C) can be normal. On an off fever
following unprotected sexual intercourse can be a sign of HIV
But with 20!!! HIV tests being negative, I wouldn't consider that temperature changes significant to doubt HIV infection. Since your last tests was more than 4 months ago which is after the window period, and they were negative too, the chance of you being infected is close to impossible.
So relax and need not worry of HIV anymore..
I would take this oppurtunity to suggest you and everyone else "practise safe sex
always" in future..
Thanks and Regards