Why do you need to change anything just cause you now know he likes you? I mean, all the explaining aside that IS what it seemed like you were trying to get at. He started liking you when you were a tom boy and all that other stuff, so now just cause he wants a relationship doesn't mean you need to bust out all GIRL on him and start wearing, like, butt loads of make up and 4 inch heels and, oh yeah, you need to STOP liking video games. I don't think you want to do that. I wouldn't sweat it. Plus your style will develop as you get older, just because you were a tom boy in middle school doesn't mean you still are a hard core tom boy, rather you just enjoy aspects of being a tom boy such as a more laid back style and enjoyment in video games and stuff. Who knows, by the time you are in university your style will probably be nothing like it was in grade 7. You can't assume that everything about who you are now will still be who you are in the future because people develop and change. Not completely, you'll still recognize yourself. But being a tom boy is ok. And he obviously LIKES that you are a bit of a tom boy. So really and truly, don't sweat it.
You guys will go on your first date and everything will work out
