1. The HIV test is pretty reliable. False negatives are extremely rare. If you are really worried, you can get tested again after a couple of months. Then you should be absolutely certain.
2. HIV is difficult to get. Even if you have unprotected sex with someone who is HIV+, there is about a 1% chance that you will yourself contract the virus.
If you know for a fact that your partner is HIV positive, then you might want to get tested again. It is always a good idea to talk to your doctor.
Other than that, it is very unlikely that you have HIV. People have protected sex (and unprotected sex) all the time. People get a flu all of the time sometimes lasting for weeks. These are very likely two unrelated events.
Hopefully you have a doctor. Go talk to them, and listen.