I can relate to the OP in more ways than I'm willing to admit. Using willpower (or drugs) to fucking get with the program IS the only answer. Buck up or shut up. I can convince myself not to get out of bed in the morning. That's my problem and no one can solve it for me except me.

Something being easy for another to do, and it being what must be done, while being hard for you to do, doesn't make it something you don't have to do.

I have been in the OP's position. In my case it was medical. It took years to diagnose correctly, and years to treat. I'm still not "back to normal". There is no way willpower can overcome a medical condition. It's like saying "I feel terrible because I have a cold" and the response is "Will the cold away and you'll feel better". I have the feeling that everyone who thinks willpower is the answer is underestimating mental heath issues.

There is no way willpower can overcome a [physical] medical condition. But if you roll 20s on willpower, there is nothing you cannot do if you put your mind to it. The problem is that people with mental conditions don't roll 20s....

That may not be true but with what little I understand of CBT, that's what I must believe.

There are lots of things you can't do if you put your mind to it. I can't fly without an external machine no matter how many 20s I roll on willpower, and neither can anyone else. There are physical limitations to what you can do and your brain is physical. As another example, someone says they have difficulty being understood because they have poor grammar. The answer "Speak properly" is not helpful. It doesn't explain how to get from point A to point B.

How should I make my self organised and responsible? Is too broad for a SE question, just as is How do I learn English? Other than offering encouraging anecdotes such as be where you're supposed to be when you're supposed to be there, and 99% of life is showing up, the OP either needs professional help, or they 'need to put the work in'.

As you say, seek professional help. If you're given a clean bill of health (and that advice is correct - it wasn't in my case, I had to keep pushing my doctor to check until it was found I had a very real medical condition that had previously gone undiagnosed), then you need to work on your bad habits.

The other answers make that suggestion. Likely I still struggle because I endeavor for the answer to be anything but drugs or professional help (which is why I like this one). VTC is both above my pay grade here and outside of my purview.

No answer should recommend drugs. We are not doctors, and those of us who are doctors are not the OP's doctor. See your doctor (who may or may not prescribe drugs, none of our business). If it's not a medical issue practice slowly getting better. Trying to get to point B in a single step from point A will most likely cause behavioral rebound.