If you've only tried using nipple clamps on yourself solo, then you may well find that it's a completely different story if a partner uses them on you. Or then again, maybe you won't, maybe your nipples are too sensitive and it just provokes the /bad/ kind of pain! Nothing wrong with having something as a fantasy, but leaving it in that realm and not toying with it in real life. I for one know of at least one fantasy I have which remains just that and (up until now at least) isn't something I have ever had interested in bringing into reality. And that's fine! For me I've found that it can still be fun to narrate a role play with your partner involving the fantasy as a form of role play. Or just leave it to the stories - up to you! As far as being "normal" goes... well, we all know normal is relative, hehe, but yes, I'd say it's very normal indeed!