I wouldn't go back to being a teenager again for anything in the world! Seriously, though, the best thing you can do is be right up front with Katie. Tell her yourself how you feel about her. If the feeling is mutual, or she is willing to get to know you better, you've accomplished what you wanted. If not, well then, you at least know the truth and can move on. If she's not the one for you- there is another one out there who is. I hope it all works out well for you.