Baylor, this is what helps me.
First, in organizing your thoughts, the subjects you're studying, the tasks you need to get to, and what aspect of your life to which they pertain, I have been using a basic version of Evernote, a freeware I found online. You can organize notes within "notebooks", and quickly click between them. So, for example, if you're in your "Subjects" notebook and adding text to your "Pre-Socratic Philosophers" note, and you suddenly realize you want to want to learn how to perform the theme song from "Raising Arizona". Your mind will do that forever, deal with it. You could type it into the relevant note, go back to your notes on Democritus, and you'll be able to comfortably delve into it because your other beautiful thought is in no danger of being lost. Do not spend time organizing how you will organize, just start using it (if it please you), and the most beneficial mode will emerge. I use a notebook for each facet of my life, and each facet has a "to do" list on the top. I can check them at a glance and decide which item to work on, which helps me delve into the task confident that there is not something else I ought to be doing.
Also, I bought a moleskin planner; it's half weekly planner and half ruled paper. It's been a tremendous help to me. I carry it with me, I have a thought, I right it down, I move on.
Also also, if I guess correctly, you need a routine. Make a list of "action categories" with the most urgent at the top. Produce before practicing piano. Clean the house before producing. Wash up before cleaning the house. Et cetera, ad libitum. Go down the list every day.
Meditation will give you perspective, but I don't think it will help you focus. Corny as it sounds, you have to love what you're doing, and that will only happen when you are focused on the task and not on performing the task. The drugs help you because they provide a short-circuit to fascination, to love. A good analogy is married sex. The mystery, so to speak, is gone, so you don't think about what you are doing... you're just doing it... there is only "us". You are only able to love something like that if you spend a lot of time on it in large chunks; partitioning your life into hourly units and fluttering from one thing to another will not help (although setting short-term goals like "I want to finish such-and-such within the hour", will). If I want to research predicate logic and restrain myself to an hour, fine. But when producing, like writing a story or a piece of music, that has to be in large chunks. Like a date. One simply allots a swath of time to be with their lover, and, with time and repetition, comfort comes and you are increasingly there with them. That's love. You can get that love with time or drugs, and yes, adderall helps... at least in the short-term. Paul Erdos used amphetamines. Carl Sagan used cannabis. However, until you have tried good diet and exercise, don't even think about it. Drugs work, but love/dedication is more enduring, and health is foundational.
In short: organize your thoughts, develop a routine, and love what you're doing. I've been in your same position and am still trying to climb out of the morass, but the Universe will have to kill me before I quit.