The thing with apathy is that you don't find pleasure or pain in the things you used to love, but you do feel this deep anger inside of you when you detect yourself rotting away and I can see that in your letter, desperation is the only thing that feels real right?
This is no time to panic really, this means its a sign of mastery over what you once held such a high prize, you've got it already. And you should be open to other stuff, you shouldn't be afraid of knowing there's a unexplored side of you waiting to get out, in fact it can be as simple as changing your routine with the same idea in mind, but you have to feel emotion to it, what's one thing you would want in that moment, serenity, quite time, love, exercise, do you allow yourself to have these things? Life can feel so rushful at times and its not that we want to get back into motion like we superficially think, but to actually feel better in that afflicted time of introspection. I believe that that apathy is a sign of your doing to tell you that you have been neglectful of your needs, desires, and turn a deaf ear to what you feel, you ignore this things you end up believing they don't matter and why should you then have them and give up on tending your being, because there's a hunger deep inside of us that can't be filled by anyone, a special time you come to see yourself in your precious place untouched by anyone where your voice is heard and truly appreciated. Tell me, isn't this place influential in every way? And if you feel good hearing this, why shouldn't you, you don't need to back up every action and statement with reasons, don't all we want is to feel good, you've in fact already made your choice, this mushy feeling can only mean we have been looking to find this all along, that we WANT this and nothing else should even matter or be added because its perfect like this.
This is in fact a sign of change you must aid to its conception and you play a major role in it, the creator. That you should engage in new projects of your desire or curiosity. Don't force old habits, they lose their juice with time and help us move on to the next better thing at times. Its a chance to know where to head next. You could be more than a musician, why stop there, there's something there that's valuable to get. And your best talent might in fact be musician, but who knows, there's something that would make you happier and give it a more active motion in your life.
And the music has happened to me soooo many times before, but I've learned how to deal with it too. When I was younger I used to have those cheap mp3 players being not all that impressive. But far from it to me, I only had one linkin park album and I swear I was ready to rock the gym or sweep the courts. And now I'm with a massive ipod classic 160 Gigas!!:O
The reason for its doing is because you try to mask your true feelings with songs that once meant something to you but you're already way past that stage and try to look for the buzz when you heard it that first time. It doesn't work that way, and it is exactly related to your apathy issue, you feel stagnant, you feel empty, listen to yourself!! Once you've unleashed yourself, you will find the music has a different feel to it, you feel higher than before because you feel the past and present, you've moved on. But its very common to dig your emotions into music waiting for catharsis, but the music isn't your going to solve deep issues, you are. It will just remind you of your stagnant state, in which I say nothing is not nothing, there is always something to us, we are human after all.
Inspiration is creative, you can't recycle your own material time and time again, search for good desires, innovation is your friend here.
As for everything being so fake, its your inner habits telling you how much of a hypocrit you are when you engage something in which you don't really believe in. After all, you've had quite sometime doing this things, but don't get discouraged, this fakeness, this disgusting feeling inside, is your past thinking and you know when you first initiated that you felt the purity of the desire...just believe in it. Its true, but the your past voice is so strong. Don't listen to it. I know the fakeness, and it will only serve to prolong time and make harder a lesson later on.