It could also vapospasam, it is very painfull and the cold weather can make it worse, try keeping it warm, use a heat pack to see if it helps.
Exactly what I was going to suggest. I was diagnosed with vasospasm when DD was about 10-12 weeks old. I had been treated for thrush twice (I honestly think I did get thrush twice though) but when the pain continued and got worse, my GP just kept on treating it as thrush. I was in agony, even when I wasn't breastfeeding. Cold temperatures made it worse too. If the breeze was cool on my face, my nipples would ache/sting - I can't find the right word. It hurt like hell anyway!!

My LC finally diagnosed it and suggested I go on medication if I wanted to continue BF. I can't for the life of me remember the drug I was prescirbed but it's for high blood pressure. Anyway, after a few days the pain had almost gone - I couldn't believe it! Within a couple of weeks, I was completely pain free. I continued to take the medication until DD was about 5 months old and I've been pain free since.

I suggest discussing this with a LC, hopefully they can help.

ETA: sorry, just read your last post. It would be unsual to get it in only one side but it can happen. Also, it often occurs in damaged nipples so maybe all the expressing is to blame. That was the case for me anyway.