2 years ago I dyed my hair black and kept doing it once a month, I decided I finally want to go to a light brown. Should I slowly do it with hair dye or go to a hair dresser?

Were you dying your whole head black once a month, or just the roots? If you were dying your entire head once a month then you probably have severely damaged hair and would be quite porous by now.

Suggest you get it cut as short as possible and let it grow out if you want any hair on your head at all. Sorry, that is the bottom line. You have been damaging your hair follicles and your scalp for 2 years now, time to mend it all.