I can definitely relate.
I don’t know if this will help or not, but you described just what I was like at your age. With time, my mind seemed to slow down a bit and then it became easier to complete one thing. For example, after being a legal secretary and then paralegal, and then taking college courses in chemistry and biology and astronomy (and buying a huge telescope that is twice my height), I went through ground flight school and did great, but dropped out. Then I started nursing school because I knew nurses could work in several different areas and it would probably keep my interest. I did one year of community college to become an LPN, another year to be an RN, and have worked my way up to be a nurse practitioner with a PhD over the course of 27 years. (It doesn’t have to take you that long, of course; you just work in different areas, then when you get tired of it and want to go back and add a degree, that’s something new you can get into). After all of that was completed, I was diagnosed with ADD, so it made more sense.
What helped me was to decide on a career trajectory that I could start off in smaller sections and then build on it. I know the million dollar question is finding out what you like and can stick with. I would venture to say that you just need a few more years. For now, even though it’s frustrating, enjoy your youthful energy, and the options that you have. The sky’s your limit! Sometimes if you pick a career that doesn’t keep your interest, you can translate your work to another area, and that might help. Pick one main thing and just do it. If it ends up not catching your interest, do something else, either through work or more school, or pick any hobby you want to do after work and investigate that. Set goals like, “if I take this job, I will keep it for 1 year, or 2 years”, etc.
The great news is that you sound very bright and will most likely succeed at any career of your choice. 🙂
Take care, and I hope this helps a little.