Recent break up

I just recently broke up with my boyfriend of almost 5 years. I’ve been with him since I was 16 and lost my virginity to him and he’s the only guy I’ve ever been with. Im very nervous for the first time I have sex with someone else. There’s a guy I’m interested in and it almost happened but I got too nervous and stopped it. What should I do and how have your experiences been with the second person you’ve had sex with? Possibly after a long relationship?