Ingrid is right. You're not really knitting in a circle, but rather a spiral. That means each new row just kind of works up and over the beginning of the previous one.
The only way to make rows truly match up in circular knitting is to wrap the last stitch of each round. This kind of "ties" it to the beginning stitch of that same round and keeps them even. I couldn't find anything in the videos on this site on how to wrap a stitch and I don't really have time right now to search myself, but I'm betting someone out there has a link or can find one that will show you how to do it.
Of course, that's not much help in the middle of a project, is it?:??