I am sorry that this happened to you and that you are really apprehensive. You deserve better and I hope that you will value yourself, inspite of the sleezbag that you had sex with. While it may seem like the end of the world for you at the moment it isn't. You are still a valuable human being who is to be treasured.
It is important that you get tested for STD's and HIV as soon as possible. You cannot deal with things until you know what is going on. While HIV and STD's are both contagious it is not a forgone conclusion that you have either
Meanwhile we are here to support you