well, you have to wait at least
6 weeks to be tested, after that you should test at 3 months. I don't know the odds, but it is difficult to get HIV, but you did expose yourself to it by having unprotected sex with a prostitute. You cannot diagnose HIV through symptoms, but take a test at 6 weeks then 3 months. The 6 week test will be a very good indicator of your status and the 3 month test will be conclusive.