I've had this problem for many years, although it's not perfect that problem is largely solved and being able to shift focus so quickly has become a super power.

When your focus shifts so often you can't develop basic cognitive functions(especially executive function). The part of your brain that is suppose to regulate focus is really funky. But I bet when you find something your really interested in your brain won't stop focusing and it feels like you have blacked out and are doing everything in "automatic" mode. This is called hyperfocus and it can be incredibly useful if you can "control" it.

You might cycle through various medications over the years, some might even cause you anxiety and other horrible side effects. But it won't actually fix the underlying problem which are structures in your brain that aren't developed properly.

Luckily there are solutions; treatments to improve your mind ability focus like Neurofeedback. Once you can focus you need to find a physically/mentally stimulating task that requires serious cognitive functions like memory, task execution, focus switching and the many other functions. I like to dance and play music. I've done a lot of work reverse engineering the brain and made incredible progress improving its ability to operate.

Don't ever that listen to that pity party in your brain. Once you cross a certain point(after A LOT OF WORK) your ADHD becomes a gift and you will never want to give it up not matter how much failure and loss you have experienced. ALWAYS remember you are different, everything about you is different from the normal population and trying to conform to their systems, ways to of thinking and working will rarely work for you.

EDIT: I will add I understand that medication works for some people and that's great. But it was largely a waste of time for me and seriously affected my liver.