Thanks for all your replies!
My concentration issues are unfortunately not due to depression, but I wish they were because then it'd be an easy fix. These concentration issues have bothered me for over 15 years and they only get worse with depression.
I'll look into Strattera, Dexedrine, and caffeine, although I haven't had much luck with caffeine in the past. Caffeine only slightly improves my concentration, but not enough to be effective.