I can't tell if I can Orgasim

Ive had sex before and my partners have told me I've cummed. But I really can't tell. I can when they do. But I like it better when they do. Not that I don't enjoy sex. I just like knowing they had a good time as well. But I'm very conserned that I can't tell when I do. Like they tell me they can feel it of see it. But I really can't tell at all. Should I be concerned? Or is something wrong? Or have I really never came and they're lieing? Or do they not know what it's like when a girl cums? SO CONFUSED