No contact is not a thing you use for a week. It's something you have to institute for a long time for yourself. What book were you reading (or messages you were receiving?) because the one I read told me that the longer you have it the better it is.
What did you learn from your relationship? I see you said "We were doing fine for a while (fighting and all)?" I know we all have this accepted view of relationships, from what we see, what we hear, maybe what our parents were like that fighting does happen. But it shouldn't. Okay, so there is passion there with fighting and passion is great. But fighting shouldn't be a normal thing and our goals should be to minimize the fighting as much as possible. I think you should have a little more analysis into your relationship. And maybe bounce a few ideas against some neutral parties (i.e. here on the forum).
I certainly know how you feel. When I first got dumped, I was in straight panic mode and through all sorts of attention at her. And it was purely panic, purely in my sole interest and in a way, it made it feel like we were still together. But we weren't and she had to re-dump me again (although she did respond to me). Letting go was tough, after I got dumped the second time, I instituted no contact and thought I could win her back from a book called "How to get your ex-girlfriend back". While we were still talking, she was seeing somebody else and I found out they were dating when I broke no contact. The point is while she may talk to you, and may even call you, she is still keeping her options open. And it hurts when you find that out, dagger right in your chest.
We all have issues, we all have problems, and you just have to realize that they don't want to be that person to fall back on anymore when they dump you (even if they play the part) because they are confused too. You just have to focus on how to get through each day without them and it's dark now but it will get easier. And yeah, I still haven't been serious with anybody and it's been a year but I have found happiness on my own without her and I think you should try and find happiness on your own as well. When you don't need to rely on somebody to hold the key to your happiness, the independence you feel is an amazing feeling.
Can a relationship rekindle? Yes, but not anytime soon. You need some time on your own to let the hurt fade (on both ends, not just you) and maybe you guys will still have that in the future. Unfortunately, if she's not ready, it won't happen. How do you know that? You don't and you can't guess it. That's why it's easier to find somebody new. Fresh start, more experience, better decision making on your part. You never know when you may run into them in the future and what can happen, but until then, try not to focus on them.
Should you remember her birthday? Let me tell you a story. My ex's birthday fell about 6-7 months after we broke up, and I sent her a text after 6-7 months of no contact just to wish a happy birthday. It was fine, fair enough. Then a few months after that, I was going to be in town and I figured we could meet up and catch up. She was all about it at first and then completely blew me off. I still happened to run into her anyway and it was a real awkward situation. She's been dating somebody the whole time we have been broken up, so maybe it was weird for her. Anyway, I believe the point of my story is that while I convinced myself that I was doing it to be nice, part of me did hope she would try and talk to me. Same with the call and the attempt to meet up. One thing leads to another and next thing you know you are falling back into old habits. And I think I really do want her to be happy even if it's not with me and I want to be friendly and with friends with her, but it's just not very likely. Depending on the people, depending on the situation, it's all very unpredictable. And I still think about her and still haven't been with anybody seriously since. If you really want to move forward, make sure you are ready before you make any attempt at contact. And if her birthday is any time soon, you probably aren't going to be ready.
Should I salvage this? No, this relationship is broken, you should view it as something that is lost. Not a bad thing, there is alot of hurt and alot of problems and issues lying beneath the surface. What you want to do is have a fresh start, a new relationship if anything. And the only way you can achieve that is if you both became different people and THEN wanted to give it a shot. Is that likely? No it isn't. But if you are concentrating on working on yourself to make yourself not only a better boyfriend for the future, but a better son, brother, friend, etc., you maximize those odds even if you don't end up with her. And that's if she has really changed as well, she very well could not. In that case you couldn't work out logically anyway. Give it some space, work on you, and see where you are in the future.
Is this stress the reason? It's a factor, but it shouldn't be the say-all. If it was, she isn't a stable person to have a serious future with. If the going gets tough, and this is her reaction? Nope, not exactly a keeper is she? Could it contribute and amplify your problems? Yes. Not to mention you aren't at the top of her priority list if her school and job are coming ahead of you. Which isn't exactly a bad thing, you want a girl that can stand on her own two feet. At least I do. It is a tough time in transition, and she may not be willing to build her life and future around you, especially if you are getting in the way of that (Does she have to find a job where you do, where you guys live, etc.). Chances are that your issues are more about what's getting in the way, and the only that can heal that is time.
Good luck with everything man, and instead of talking to her about your problems, try and vent on here. That way you won't say anything you shouldn't have said. I know it's no consolation, but you have to utilize every tool at your disposal as long as it isn't putting baggage on her. She wants to be with somebody that is attractive, which isn't you if you are moping around and having serious problems to talk to her with. She wants to be with somebody that is stable and can provide for her, in the same vein as the attractive part. Find happiness on your own and when she sees you again, it's a whole new you, eh?
Waking up next to a beautiful girl,
Step outside and say hello to my beautiful world.