Struggling with learning disability. Advice?

So I’m 21, and I have adhd, it is really hard to deal with and I’ve never really accepted it, I dropped out of high school because it was so hard, I was ok with the other subjects besides math. I was in special ed and I moved around a lot back and forth to mom dad and grandma, and the high school I was going to go to I couldn’t because I didn’t live in the area and the other schools by me didn’t have special ed, so I went to an alternative high school, but that didn’t help much either, Well I Just Found Out About a online school by me and I want to sign up, I’m just scared I will fail, does anybody know of any medicines or anything I could use to help me?