This "just a phase" thing....legit or just get over it.? I need some happy ending stories please??

So...here's my story: we've been together 3 years, 4 years August 7th...we planned EVERYTHING together, from marriage to kids, he talked to my parents we became part of each others family...we went on trips together, just overall loved one another.  Our future wasn't a maybe, it was expected...and after all that, tech school has changed his mind...In a matter of DAYS he went from loving the idea of us and OUR future, to wanting to hang out and party with his "brothers."  I was supposed to go down this weekend, and for a couple of days it had been a little rocky.  Mind you a week before this he COULDN'T wait to see me...he still talked about our future, our upcoming road trip to North Carolina, getting engaged, the works.  But once he hit phase freaking 3 he went wild.  He didn't call when he said he would, he didn't know wether or not he still wanted to get married anytime soon, he all of a sudden was "too young" and HE WAS THE ONE WHO KEPT TALKING ALL ABOUT THE FUTURE!!! He couldn't wait...and now? All he cares about is having fun and hanging with the guys.  He goes from missing everyone and wanting to come home to now being totally fine and not missing anyone?!!  I'm racking my mind trying to figure this all out and everyone says every guy goes through this at tech school.  So what do I do?  I give him his space...I stay supportive, say "Have fun"  "Love you"  "It's okay, I'm not mad" I put EVERYTHING into trying and make it work and what does that get me?  Nothing, absolutely freaking nothing.  I asked him if he still wanted me to come down there, he made excuses and kept not answering my question and then finally I said enough.  Do you want me to still come down or not?  And what did my perfect little airman say?  "I don't think it's a good idea..."  How are you supposed to react to that?  I said for 3 years I have been here for you and for months I have been supporting you, writing everyday, telling you everything is going to be alright, and after all that and 3 years of my freaking life you can't even spare 3 days?  Nice to know, that in a couple of days everything you ever thought possible flies out the window.  Everyone keeps saying it's a phase and once he comes home he'll see...but you know what?  I have NO idea what's gonna happen...I swear when I say he was the IT guy...he really was.  He promised 80 years and matching rocking chairs...he told me no matter how angry I got or how much I wanted to call it quits sometimes that I was stuck with him forever...he brought me flowers for no reason, reminded me everyday how much he loved me and how lucky he was and in a FEW days everything changes?  Explain how that is fair and how understanding do I have to be now?  I gave him everything...support, love, everything and this is what I get....it's not just me either, he's been treating his whole family like crap...so please tell me...PLEASE PLEASE PLEASE tell me, how supportive I should be now?!  You know the pathetic part?  I ended it by I saying I was done, so tell me why I am still praying this is just a phase and he'll remember who we were?  Since we've gotten together I have never seen anyone else...it's ALWAYS been him...Always.  So here's my question to ya'll:  is it a phase or has he changed for good?  mind you it seriously changed in a FEW DAYS!!!!!!!   Oh and you know how everyone tries to say he's under alot of stress and it's totally different I just have to understand?  My dad was in the air force and is now retired and has explained the whole thing to me...I know I will never be able to understand fully what he went through and I get that these new friends do, I get it, I really do.  But seriously, is there anyone out there with a similar story with a happy ending?!  I just need something right now... : (