i'm 19 weeks and mine have been intermittently sore and extremely sensitive since about 15 weeks, very uncomfortable but bearable.

there is a thing called raynauds (sp?) syndrome that is caracterised by the nipples looking white when they are painful, made worse by cold. It can be treated with medication and is often misdiagnosed as thrush in the breast.
this is a transcript of an interview which explains the symptoms a bit

http://www.abc.net.au/rn/talks/8.30/...s/s1181487.htm

nicca