It is highly unlikely that the virus would have been able to replicate sufficiently in a 3- or 4-day period to infect another person. However, you should refrain from unprotected sexual activity with anyone until you test conclusively negative for HIV. In the unlikely event that you test positive for HIV, it is your moral (and possibly legal) obligation to tell your girlfriend. However, as I said, it is highly unlikely that you were infected and that you could have infected your girlfriend that quickly.