When I was 15, I was at the top of my game. I had mastered this writing thing, I knew all I needed to know,I wrote steadily. I was The Writer.
...except, I wasn't. My format was a mess, and so were most of my stories. People read them because I loved them, I loved writing, and sometimes the passion carries you where nothing else can.
You're worrying about formats, about problems, about trying to sell it. You say that the only thing that gets you through is that you think your story's great.
Good. Keep thinking that. Remember, you are writing the single greatest story that has ever been written, in the entire history of the world, and after reading it, the rest of us will lay down our pens and walk away.
...unless it's not. But even if it isn't, then this next story that you're starting is whiz-bang the greatest thing
ever since the dawn of time, etc.
Love your story, love your writing, and keep that foremost. Everything else will take work, stress, and pain...but the love will get you through so very much of it.