I think the actual meaning of "I love you" has been somewhat deluted. From my own experience it's not something you gain after 3 weeks. What most people feel is just an attraction towards one another... usually a crush, or some type of lust.
Love really can't be described. But it's one of those things where if you REALLY do love someone... you'll know it. I think it's one of those things you say to a girl you could see yourself staying together with for a long time. So highschool "love" is not usually actual love since very few people make it out of highschool together...
The best advice anyone can give you is to just follow your heart.
