Hello~Dr Google is really the last place to look for help, I know, it gets me uptight all the time. Anyway, HIV and other sexually transmitted diseases don't just appear overnight, so, I doubt if that is what you have. The little itchy bumps could be a form of stress hives. I would honestly see a GP, this will probably be the only way your mind will be set at ease.
Is there really anything that a stranger on a website can say to you to make you chill? So go to a clinic and tell them you would like to be tested. Then go onto U-tube and learn how to use a condom.