I guess the big thing is to work with your mental health care team to figure out a treatment plan. Medications for ADHD do work pretty well; I started Adderall and, shortages notwithstanding, I find that it works for me and my body tolerates it pretty well, but your mileage may vary.
Regardless of whether or not you start medication, though, consider therapy or counseling to build better strategies for improving your focus. What I found is that Adderall will help me focus, but not necessarily help me focus on the right thing. Improving your attention span is half the battle, the other half is breaking bad habits and building new ones that help you get things done. For me, my ADHD is coupled with anxiety, so managing my anxiety and building confidence was key.
So yeah, I hope that helps at least a little.
I'd recommend working with whomever diagnosed you (or having them refer you to someone) who can help you figure out those answers.
I never had much luck with other drugs because of seeming inevitable tolerance problems and side effects.
Secondly, knowing your status is a large step in the right direction. You can build routines around the things that seem to slip from your consciousness. For example, patting yourself down for your usual items before leaving in the morning, or making a habit of capturing everything you learn in some sort of notes application for future use.
I'm in the same boat and am at the point of NEEDING medication so I sympathize and wish you luck.
I suppose you’re struggling with something which is why you got a diagnosis. So try the medications if you want, start low dose and only increase if necessary. If coffee really helps, then a stimulant is probably a good starting point. You may find some doctors who are really hesitant to prescribe them. If that’s the case, find a new one who is willing to help without making you do a little dance for them. I’ve heard horror stories like requiring the patient to submit to drug tests, in person visit to get a refill, unwilling to prescribe more then 30 days at a time, etc. There’s no legal requirement for this in my state and probably none in yours.
Being diagnosed just means you have a more informed world view of who you are and things to watch out for. Have fun and stay weird!
If it works for you, keep doing what you're doing.
But don't forget to get in touch with nature: go for walks, go for swims, go for bike rides.
Being diagnosed with something doesn't change who you are, only confirms who you are, and that's part of who you are now, only legally diagnosed.
Personally, I couldn't keep a job for years. This led me to realize I had ADHD and get diagnosed. You seem to be successfully running a company, so you might have developed the good coping skills to deal with your limitations already.
I recommend reading Taking Charge of Adult ADHD by Russell Barkley. It's a good first book for people with ADHD and can answer a lot of basic questions about medication, therapy and feelings you might have after being diagnosed.