It is not IMpossible to develop HIV symptoms so quickly, but it would be rare at 3-4 days. You are correct in that it usually takes 2-3weeks to mount an antibody response. If you are still concerned however, you can ask your doctor to do an hIV RNA PCR (viral load) test. Also, have you been checked for other things, like gonorrhea? This would be higher on my list of diagnoses than HIV, but it does sound like you have a garden-variety flu.