How can i be sure of having safe sex?

I am still virgin and never had sex. I am only 18 and i want to experience it now but i am scared to get a girl pregnant. What can i do to avoid having a girl pregnant? I also heard that with just a precum a girl can be pregnant. I want to have sex without using a condom. How can i also be great with sex? If i will have sex with prostitutes will i get sick? i don't want to have STDs