How do you know if you've orgasmed!?

I just started masturbating for the first time about a week ago. My friends had encouraged me to for a while, since no guy I've hooked up with could make me climax. Some of them were pretty bad, so I'm not surprised, but some paid a lot of attention to my little girl and still nothing. I thought if I masturbated, I might be able to make myself orgasm but I've never felt like I "finished." I'm beginning to wonder if I've orgasmed and just didn't notice, after all I don't know what it would feel like. I feel bad for the people I've hooked up with, because I don't want them to think they couldn't satisfy me, but I also don't want to lie or fake it. So what does an orgasm feel like, physically and mentally? How do I know if I've orgasmed? And—to get a little technical— is a female orgasm always accompanied by cum?