How Long Before I Can Focus?

In high school I was very smart. I graduated early with a 3.8 GPA. All I did was school work. Reading, homework, etc. I never went out. As soon as I graduated I went to college. I wrote some amazing things, and I was doing great. However, I became addicted to methamphetamine. I got arrested and lost everything I had. My home, my car, my friends, my family, everything. I dropped out of college. I have now been sober for a year and I am wanting to go back to college. But when I tried this last semester, I couldn’t do any work. I couldn’t focus, and I couldn’t do simple things that school requires people to do. I couldn’t spell, add, subtract… and it was very hard to deal with, considering I used to pride myself on being intelligent. I’ve registered again, but am still afraid the same thing will happen. It causes me to have panic attacks and I’m having a hard time with depression. How can I deal with the anxiety of going back to school?