I can sort of relate.

The concept of nudity itself doesn't really bother me. It does however, make me pretty uncomfortable when I'm in the presence of others. Sex, however, invokes the same reaction you describe. On more than one occasion I've been watching a TV show with the family and when a sex scene shows up I'll have to excuse myself to go and quietly freak out in another room. Punching the air, punching a pillow, anything to vent.
My advice is this: look around your area for a therapist to talk to. I believe you when you say you were never abused or anything like that, but talking to somebody can really help you as far as figuring out why you feel the way you do about nudity. It could be something you'd never even consider. Maybe your bf could come along, maybe not. Your call.

You say this is interfering with your everyday life. If so, than it sounds like it's time to start looking deeper into the issue. I hope you find some resolution.

Good luck!