Somebody help me please, I need to know how to tell this girl?

ok, so me and this girl have become very good friends throughout this year. but secretly along the way, i have liked her as just a little more than a friend. but now since the school year has ended, i asked her to go to a theme park with me and she said yes:) so we went 2 days ago and had lots of fun! but now ever since i dropped her off at home that night, i cant eat or sleep without thinking about her. i have dreams about her when i do sleep, its just a very overwhelming. i fell in love with her at the theme park. but now all i have is facebook to tell her how i feel becuase she is going on a vacation and i dont know how long, i think about 2 or 3 days. so im planning on sending her a facebook message (becuase its all i have) to tell her how i feel. i just do not know how, i dont want to lose her as a friend! i dont know if she likes me more than a friend or not but i guess if i tell her how i feel the right way, she will tell me....please help me somebody, i cant take this stress anymore