I have a four year old daughter, and when I was pregnant I read that breast feeding could cause orgasms, and that a lot of women felt guilty about it. I think it was because of that, and because things ended badly with her father who I, erm, associated with my nipples!, that I didn't want to try it. In the end I did do it, for the first few days, but it hurt like hell. Perhaps if I'd persevered it would have got better....I guess my point is, good on you for continuing to do it even though it may have weirded you out. I don't think you need to worry about it; it was purely a physical thing that stimulated your nipples. Lots of things could have done it. And besides, what's done is done. Just don't talk about it with your friends if you don't want to; you don't have to justify yourself.