Kind of a strange story, don't you think?  But it was the fact that I made a mistake but felt the guilt for it.  I didn't do it because I didn't care... sometimes things happen, that stop us from doing something.  But it's the fact that you can show guilt and sadness from hurting someone that can make ALL the difference, don't you agree?  His ex... did she do it more than once?  Did she do it over and over again?  She she ever take the time to sincerely apologize and explain the situation as to why the call was never made?

So, it's time to talk to your boyfriend.  Time to explain what happened, and let him know that you apologize.  Let him know that if it hurt him, you never meant to, and you would do anything to go back and get the chance to give him that phone call (as I'm sure you would).  We all make mistakes, and sometimes, we're not there when we need to be... but we're human, and that's expected.

And now.. why are you both scared?  Do you care for each other?  If you do, then you should have no reason to worry.  If you truly think he cares about you, then why do you fear that he will leave you?  And the same is for him?  Talk about your fears, talk about your worries... my boyfriend and I sometimes discuss about how we're scared we'll go our separate ways some day.  I'd never want to leave him, but things change... emotions, feelings, personalities, lifestyles... and sometimes move us apart from one another.  But if you spend all your time worrying, then you never get the chance to truly enjoy a good then when you have it, right?

If you both care for each other, if you keep your communication strong, then whether you're at camp, and he's at college, it shouldn't make a difference, don't you agree?  Maybe a honest chat with him will help clear up both your worries :).

Best of luck, alright?  Wish I could have helped you out some more :).