You've got to learn to stop worrying and thinking about it all the time. There are lots of great replies already, so I wont add any more. We've all been there and done it, and we all know how hard LDR's can be.
My first LDR was a failure, and like you I was stressed out all of the time, thinking far too much about it and not fiding something else to occupy my mind.
I learned from my mistakes and my second LDR is much easier, although that is probably down to having a great girlfriend who I completely trust this time. In the 8 months we've been together, I don't think I've ever got stressed, depressed, had bouts of thinking if its actually worth it. I've got a great girl who I chat to every day, we tell each other everything, things that make us happy, what upsets us, what stresses us, what makes us jealous, all about our previous lives and relationships.
To sum up, I don't need to get stressed, I completely trust my girl, I don't need to know her every move of the day because she's genuine, and i don't worry about what she's up to and who she is with. If you really love your girl, and know that she genuinely loves you, you communicate well and are totally honest with each other, LDR's are a lot easier
