Mine aren't sore, more super sensitive to touch (and excruciating to feed from I found last time!) but I can well believe that for some people it's one boob only, and probably that the feelings come and go. Just a quirk I think, pregnancy is pretty weird in the effects it causes.
Just a tip for when you speak to your GP Lynsey, make sure you are clear with them whether it's anti nausea or anti vomiting meds you need. I got given anti vomiting ones in my first pg which were no help as I was only being sick once a day, - it was the nausea that was so debilitating. If your GP won't prescribe, try another GP, - this is one of those things where some GPs are more helpful than others. Weight loss, dehydration and general incapacitation are usually the triggers for medicating and these can be caused by either nausea or vomiting.
Here's a bit I've C&P'd from the hyperemesis thread on the range of meds usually used:
cyclizine (old fashioned anti-histamine; can make you sleepy)
Metoclopramide (empties the stomach faster, less to upchuck)
Domperidone (similar)
Prochlorperazine (stemetil/Avomine/Buccastem) (works on your sense of balance; also a travel remedy; can be very good for some people).
Promethazine (called Phenergan)(stronger old fashioned anti-histamine, also sleepy-making)
Ondansetron (the strongest and many people find the best, but causes constipation).
I'm on avomine (which I think you can actually buy over the counter for travel sickness anyway) and it's helped me a lot. I'm feeling a lot better now and trying out reducing from 3 to 2 doses a day.