My natural hair color is medium/dark brown I wore it light blonde for years, I got very tired of dealing with the roots and up keep so I had my hair dresser dye it brown, well that faded so I tried a semi perm dye that has lasted about a week so far and is fading fast, I thought the color was beautiful before it started fading, so my question is how often can I use a semi perm dye?

What you're probably using is technically called a "demi-perm", I think. If you mix two ingredients, then it's a "demi". Otherwise it's a "semi".

You can use "demis" every two to four weeks. I wouldn't use it more often than every two weeks. You will eventually accumulate some dryness and damage with this product.

A true semi isn't recommended for hair that's gone through a "tintback".