I have had nipple pain for several years. It only occurs when/after sweating. I don't think it's related to running cause I'm not physically active. I also have health anxiety and are sweating very much. When it occurs and the pain is severe the nipples turn almost white..
Since I've had it so many years I don't think it's 'life-threatening'. I do not think it is 'runners nipples' as well..
What can it be?