Black box dye to natural hair

Hello everyone!  *boo*

A few months ago I decided to do something crazy ( *ott*) and dye my hair black brown. It turned out darker than I expected, but I turned out liking it. (I've been using Syoss Oleo 2-10.) I've dyed it about 2-3 times myself (mainly roots) and it has been dyed at the hair dressers once.

Everytime my hair has been dyed, the hair dye started fading fairly quickly and after a month, I was fully back to my natural color. This is why I thought doing something like this wasn't a stupid idea. "It would probably fade in a month". (Spoiler alert: NO IT DOESN'T!)
I think it still fades fairly quickly. I have this spray for my roots so I don't have to dye it that often, and after 1-2 months, my hair is already a very dark warm brown in most spots.

I want to go back to my natural hair color (very hard to describe the color, but it's blonde-brown-gingerish). My hair dresser has always told me that bleach is a no-go for my hair because it's already very dry.
Before this, the hair dresser had dyed my hair ash brown with highlights once, but that's probably a year before I dyed it black.

Is there any way to get to my natural color without having to bleach it? I don't mind it taking a lot of time. I'm really desperate, because I don't want to have the struggle of having to touch up my roots this often for the rest of my life...