Look into Raynaud's phenomenon
I got sore nipples during my first pregnancy, particularly when I was exposed to cold. It went away after a while and thought nothing of it until baby was born and had trouble (VERY painful) breastfeeding and was diagnosed with Raynaud's phenomenon/syndrome/disease.
It felt really weird, and looked hilarious, but I found filling two bowls with warm water, putting them on our kitchen bench, and standing with my nipples in them really helped.
Also breast pads made of polar fleece (I was lucky enough to have a friend who sewed, but look on ebay) also help keep nipples warm.
But Raynaud's would not cause discharge or itching that I know of.
Hope this helps