When you feel as if one of the main things getting you up in the morning is the aspect of talking to them that day. When you count the hours and days until you'll next see them. When you count the hours until you can talk with them/email/chat with them again. I've experienced all of these, and my long distance boyfriend of nearly two years and I said our "I love you"s within a month.
Check whether that person whom you are in love with is also asking these sort of questions ...
The signs of falling in love in a long distance relationship is to call each other frequently.