Read your post and I had the exact same pain when I started breast feeding. Sometimes it was like a sharp stabbing pain like needles and sometimes only in one breast! Like you I had alot of milk - no one seemed to understand what I was talking about and like you everyone said I had thrush, but I didn't.
I can tell you to carry on BF, this eventually disappeared and I am still BF my DS who is now 15 months old and we are going strong with no end in sight.
Hope this helps