When you really stop and think about it the whole dating game is ridiculous. Both parties are doing their best not to appear too interested, both hide their true feelings and everybody is damaged due to past experiences so nobody wants to break down the walls their hiding behind.
Word of advice Blackdog, you worry too much. If you generally feel love for her there's nothing wrong with saying that. Even if you don't plan to be together forever. It's about the moment and in this moment you love her, so why not enjoy it while it lasts? Why hold back and worry about the future? You can always settle down later and even when you do, after having lots of experiences with other girls, there's no guarantee that the relationship you are in then will hold out indefinitely. Even if she doesn't love you back, it might hurt but it's also a reality check for you. So my advice, it's better to have loved and lost then to not have loved at all!