An more on topic with writing music... have you tried using a notation software? I don't compose often, but I can copy things like a movement of Beethoven sonatas in a few hours. And a nice side benefit is that it is great for your sight-reading too, especially if you aren't very good to begin with.
I don't know for sure if you are talking to me or not with this paragraph, but yes, I do use notation software. And, I just have to be clear that it's not that I can't read and write music, it's just there has been some kind of block for me with some aspects of my relationship with music and the piano and how that translates to dots on a page, for example. I mean, I "get" the notation (though I am not currently the world's most amazing
sightreader -- yet), it's just that I spent a number of years (about 10 (from about age 2), actually) on my own, mainly just improvising and playing by ear (though I could swear I read a portion of Fur Elise when I was young), before I was able to have a teacher.
What that means in my case is that I had my own relationship with the instrument, and my own relationship with the sound (involving a pretty heavy dose of my own imagination as well, as in, these things meant pretty specific-to-me things by that point), which all happened to be fairly developed before I had to start trying to connect with dots on the page as "music" in formal lessons (and by that time it was some kind of torture starting in a method book, repeating middle C, alternating hands (*pulls hair out just thinking about it*)). Reading the page has been a pretty intellectual activity for me, whereas
music and the piano have been, for me, some kind of *completely* different land than that altogether. I am just starting to be able to really connect it all together in a way that makes sense to me through and through, but I do think that writing and transcribing more music would help.