This is normal. Nipples get erect when they are stimulated.

Your doctor probably doesn't think anything about it. ;)

Well it's not just when he touches my nipples, it's when he's touching my actual breasts. It might be percieved the same way as when a man gets an erection during an examination.

It isn't perceived that way at all. Doctors actually look at breasts and hoo-has all day long - as it tends to be their job. Your doctor is not thinking of you sexually at all. Nor is he considering that you are getting hard nipples for him.

Some women cannot think of being touched physically without reacting, whether they react vaginally or with erect nipples depends on the woman. Also the doctor's offices can be cold. Maybe your breasts are reacting the the cooler air?

Trust me, this is natural.

Yeah, it's just a reaction. Thanks.