Im only 18 and im stuck with the biggest problem off my life.

4 years ago in November, i was seeing this girl called Amy. At the time i didnt think much of it as i was still quite young for proper realtionships, 14 to be exact. I did really like her, but at the same time took her for granted a bit.
She moved to California... I dont know weather it was the fact that i couldn't have her, or that i realised how amazing she really was (she is incredable), but i spoke to her every night for 2 years on the phone until the early hours of the morning. This obviously created huge phone bills and failing at school (ive got pathetic GCSE's to prove it). Im not blaming her for this at all as it was my choice but it really did screw my sleeping up.
After the first year, she came back for summer holidays, that was a very good summer for me, lets just say she obviously appretiated me keeping in touch with her. It sucked saying bye to her but i was prepared for it. She didnt come back the next year, aparently hawaii was more important. In turn i stopped talking to her so much, stopped telling her how i felt about her and even atempted to get over her, trying all diffrent tactics, from talking to her as a friend to telling her to get out of my life.
If you havnt guessed by now i am in love with this girl. Ive had realtionships since shes been gone and so's she but they i always love her, and trying deny that love by forcing myself to like someone else just fails every time.

So, my problem. She came back in summer (2 months ago) for 2 weeks. She slept over on a couple of nights, we didnt do anything but we also didnt get a wink of sleep; just spent the whole night talking, and being very flirtatious (getting extremly close to each other, touching ect ect.) This made me realize how much i love her again, which has been majorly screwing me up. My best girl friend has been telling me to stop being an idiot basicly and get over her asap as im only a months away from going to training for the British Army and ofcourse, she lives on another continent! But i know deep down and from previous experience that i wont be able too. I still love her imensly and nothing can change that. The last night she was here i told her that i still loved her and she said it back folowed by a lot of very passionate kissing.

I just got off the phone to her and I cant stop thinking about her, when im with her or talk to her im so happy, and when im not, i just think about how amazing she is. I dont know anyone else that has been through this, hence why ive not told anyone but my best friend. Since she want back too America ive not really told her i love her but she definitely knows i do.

I've wanted to be in the army my whole life and am very close to going to training, but of course i wont be able to talk to her for about 6 months. If she promised to stay with me forever then i'd drop my career in the army there ad then, just to give you an example of how much i love her.

What do i do? TRY to get over? if so how!? any other suggestions would be greatly appreciated.

thanks

Thanks