Odd that this post is here, I have a somewhat similar experience. But I believe I know what's causing my issues. First off, today I just went from 10g to 8g (I was pierced at a shop with a 10g needle). I only had my ears pierced once (when I was 19-20 and was drunk and for some reason let my drunk friend pierce me with a terribly cheap gun in an environment that was far from sterile)...anyway, I digress. My old piercing ended up infected and painful (surprise) and it was removed after a month or two.
Now, being 7-8 years later, I still had scar tissue in my left ear. When I got my new piercings I had a concern that it would be a bit worse to deal with than my right. When it was pierced there was definitely more sting, and now with stretching there was definitely more pressure/discomfort. It was only for a moment and after it was over it quickly subsided, but I do have to wonder if this will be a consistent issue with my left ear.
As far as being uneven. When I look at my ears I keep wondering, "Are they even?"...sometimes they look a tad different, other times they feel like they are uneven. But ultimately I think it's just because my ears aren't identical and so it's merely my anatomy that makes them seem uneven, because really it appears that the positioning is pretty good when I really analyze it.