Any suggestions for sites where I can improve my spelling?

So i just graduated college, summa cu'm laude, next stop medical school, and my IQ is 135, and on my best days I can solve a rubix cube in less than 50 seconds. Anyway for the life of me I struggle when spelling some words that sometimes i think i should know how to spell ...like "conscientious" and "preferably" ...I think i am mildly dyslexic or at least spell check has been bad to me...plz help any website where I can basically practice spelling?