Instead of telling you that you would never be able to be independent, your mother should have tried to find ways to help you become independent. Unfortunately, that didn't happen and now those thoughts are molded into your thought process. It can be tough to overcome those thoughts, believe me I know, I STILL find myself falling back on those negative thoughts that my father molded into my thought process when I'm stressed out or depressed. But you can overcome this.

I like the advice someone gave above, do your studying in shorter chunks of time. Additionally, try to get into a schedule where you study the same times each day, in the same environment. If you drink coffee while you study, always drink coffee when you study. Also, when in class, always try to sit in the same seat (or at least the same area of the room), and the same with the coffee. If you have coffee before a class, always have coffee before a class. All these tips help you to remember things you've learned. I practiced all of these when in college and they really worked for me. All of this might not work for you, but experiment, and if you find something that works, stick with it.

Most importantly, please try not to be so hard on yourself. In my late teens I was in a horrible place. No high school diploma, no job, suffering from severe CPTSD, I spent several months living in my car, often went days without food. What saved me was the Air Force. That gave me a job, structure, food, education and the opportunity to travel for over a decade. When I got out and went to college I was terrified that I would fail, but did well. Professionally, I do ok, not the best I could, I think in part because of my CPTSD, but I've done ok, I have a home and family and job, and yes my financial outlook for retirement sucks, but all in all, I consider myself lucky.

You have a driving spirit. I've seen it in your posts about starting your own business. Back up a step, look at all you want to do, and work on it piece by piece. And when you get down, look at what you've done, you've found a way to survive with very little help. There are a lot of people out there that wouldn't be able to do that. You are resilient. You have a tough road ahead, but you can do it. Don't give up.