Prostate orgasm - how?!

Hello everyone, in my case I’m a virgin guy, I used to play with my ass introducing small stuff but never had a prostate orgasm, until a few months ago using my middle finger and a lot of lub, I start feeling my middle finger inside, moving it round, then start getting in and out slow and then fast, it make funny noises and that makes me feeling arouse a lot, then comes the pee feeling and I letea myself go with that, then I cum with no erection, it feels amazing, my dick is completely flaccid