I don't write, but I have. I am a musician, and an abstract creative thinker. I know where you are coming from. I have ADHD as well. My inherent abilities are what make me and my art who I am. I avoided ADHD meds in the past because of how they affect my mental processes, that actually "are" who I am, mentally and creatively speaking. Alcohol, marijuana certainly enhance, in a certain way, how I approach my craft. But I don't believe that the substances ever "added" to what I already possess...my experience and my opinion. Sometimes there is just a dry season, and they can last for a bit. I agree with the idea that "forcing it" won't make it happen. It has happened several times with me that, when I just let go, did it for fun and didn't "look" for anything to happen, things started to happen. Think back to why you do it. Maybe even walk away from it for a few days...hope this helps.
Alcoholism