Yet another girl asking for 'love' advice.. Grateful for any help :)?

Well if it's a case of either telling him online or not telling him at all I don't see you have a choice, and you can always say you wanted to speak to him in person but won't get the chance now. Its the end of school, this is your chance before you both go off into the world so make sure you tell him. And I don't think his reaction really matters too much, the fact that you had the courage to do it is the important thing. You never know, him 'waiting for the right girl' could be him waiting for you. But yeah telling him is the important thing here, his reaction you can get over if it isn't what you wanted, but if you don't tell him, you'll never get over that.