Gigi, I personally never like to see my ex-es move on. Even if I don't want to be with them any more, it hurts to realize I'm replaceable, so I think I understand where you're coming from to a degree. Is your reaction a little immature? Yeah, probably. But that doesn't make you a bad person, and I even think it's kind of a natural reaction to the end of a long relationship.
I would lay off the UGLY comments on the new gf, though. That comes off as bitter and mean, not hurt and confused. (Even if it's true.)