Dark brown to blonde to light brown and now want natural color back or HELP!!!!

Hi
I had my natural dark brown hair dyed to a light blonde shade a few years ago, after a while I got tired of the blonde and went to a salon to have my hair dyed to a brunette shade. The hair colorist first applied a filler to my hair and than applied a light ash brown semi-permanent shade to my hair. At first the color was a beautiful dark medium brown. It`s been a month now and the color is starting to fade, it`s too light of a brown and I don`t like it. Now all I want to do is go back to my natural hair color or a shade close to it . Any brunette color that won`t fade or have to touch up at the roots later on as my hair grows. What should I do? Should I do this myself or go back to a salon and spend more money?
Thanks