desprate 4 help bleaching for 15 years

As long as you don't overlap your bleach and only bleach your hair once the hair shouldn't get that damaged.  To help tone down that brassy yellow try a purple conditioner.  I think the color you have now looks good on you.  Try some deep conditioning before you chop it all off.  Leaving conditioner on for 30 mins or more I find very helpful.  Good luck!

Rebekah

15 years of bleaching... wow. i've been doing my hair blond for about 6 years now and i'm sick of wasting the money and having roots all the time. i'm going to grow out my natural colour.. maybe you should consider this too..just a suggestion.

I don't think you need to chop off all of your hair, but you should definetely get rid of the split ends.  Since you bleach your hair on a regular basis, I recommend you have your ends trimmed every two to three months.  Since hair grows about 1 cm per month, you should still be able to grow it out by trimming about 1 cm of your ends that often.  If you don't get rid of your split ends all that'll happen is they'll keep rising towards the hair shaft and that means you'll have to chop off your hair the next time you get a hair cut, so better to get trims more often to prevent them.  If you want a nice short hair cut, you should try Jennifer Aniston's cut at the end of season 7 of Friends, where it wasn't too short, but just beginning shoulder length.

You should be aware that when your hair is chemically processed you should always hydrate it.  All it takes is a clarifying shampoo and a deep hydrating mask or conditioner.  L'Oréal Professionnel (www.lorealprofessionnel.com) came out with a line called Absolut Repair which is amazing!  I'm using the shampoo with the masque once a week and my hair is silky smooth (and you only need a small amount of product, so a 250 ml container will last you a while). Another line you should consider is the Resistance from Kérastase (www.kerastase.com).  Try their shampoo (Bain de Force) with the Age Recharge masque once a week.  You should also keep washing your hair to a minimum, at least until it's healthy again (yes, bleached hair can be healthy, it's a matter of treating it).  Try that for a couple of months (wash hair only twice a week and deep condition once a week).  After that make sure you maintain it, deep conditioning it every 10 days or so.  Only then (after two months time) should you color your hair again.

Now for the color, I suggest you dye your entire hair a dark blonde (number 6).  You say your natural hair is black, there's a difference between black hair and a dark brown hair, so make sure you know what your natural hair color is, that way you'll know the ending result.  If your hair is truly black, then I suggest you use a medium blonde hair color (number 7) to get a number 6 (dark blonde).  That should be your base color, then if you still want to go lighter you should add some highlights (very thin ones if a natural effect is what you're going for), which you could then put a light blonde (number 8) over it.  If you don't want a coppery result, then you should stick to ash colors.  Meanwhile, you could try using a non permanent hair dye just to get by (those dyes that come out after so many washes).  Or you could try using the Silver shampoo from L'Oréal Profissionnel twice a week to keep brassiness away.  What brand of hair dye do you usually use on your hair?

Remember this is only my opinion on the matter and I should warn you I am not a professional, however I have taken a couple of classes on hair care etc.  Hope I helped you. ^^