Highlights gone very wrong

Ok so I've always had dark brown hair(natural color) and I got a little tired of it so I thought I'd get some highlights. I was thinking a natural looking brown a couple shades lighter than the rest of my hair however when I got to the salon I was told that I should go much lighter than that and that it would come out much better compared to my complexion and being a little too easily influenced I believed it and got the blonde highlights as suggested. After my hair was done being dyed it came out with bright yellow highlights and I was completely horrified so I asked for it to be fixed. I ended up with highlights of a darker blonde shade and I thought it looked decent enough so I kept it that way. However, now that a couple days have past I have noticed that it has faded a bit on the bottom into a very light blonde color that looks gray in comparison to my dark hair and at the top the color is still rather bright, although it's more of a golden color. Also, some of my hair got lighter as a result of the highlights and it is now mostly brown so there is barely any of my natural color left anywhere. I really regret getting these highlights. This has become way too stressful and now I would just like to go back to my natural dark brown color but I don't know where to start so I thought I'd ask for advice before I completely destroy my hair. Help please?