is it a bad thing?

Hello.. I'm 17 and I've never had sex so i don't know much about it.. I've heard that if the guy comes quickly, it's not good. why? is it bad if the girl comes quickly too?

btw, is it true that guys don't like unexperienced girls? the older I get, the more ashamed I feel about being a virgin but I know that if I just did it with someone who I didn't love, it would make me feel disappointed and useless..

I'm still in love with my ex. he doesn't feel the same way about me but he said that if I ever wanted to meet him just for sex, he would meet me in a heartbeat.. what should I do? I mean, I know I shouldn't.. but I still love him.. and a part of me hopes that if we would do it, he would love me again.