Wobble, perhaps you are a law unto yourself... perhaps the law is written on your conscience and heart? (such as the gentiles were, who Paul spoke about) Perhaps this keeps you from sinning (doing wrong). But if you're judged, you'll be judged on the basis of what you have/haven't done.
The whole thing about Adam is that sin entered the world through him. Because before he sinned, there was no sin - simply because he was the first TO sin. Now sin is in existence and so in the world, and I can't say that it isn't in our nature to sin, because I believe that it is. People usually have to be taught right from wrong, as children. Taught not to hit, to steal. Taught to share, to be kind, etc... we aren't normally born knowing and doing these things, and for the most part at first, we're dependent upon our parents to know right and wrong, in order to teach it to us.
Sometimes when I think of inherited sin from Adam... I think of a parent teaching their own mistakes and failings to their children. (an extreme example would be passing on racism from parent to child, or one generation to the next generation)