I dyed my hair with a box dye and the color never showed... 3 weeks later I tried another box dye and now a chunk of my hair is badly broken off... what happened?? What do I do??

I think it's due to the amount of time between the first time you dyed it and the second time. Since in hair dye there are really harsh chemicals you probably over loaded them. What you should do is not dye it anymore and go to a professional to see what advice they could give you. I know Great Clips or other chains like the one I've mentioned can really help and they're cheap.
Try to research hair dyes that contain less harmful chemicals I know at sally's they have a wide variety of them that would give you a rich color and not damage your hair.

Thank you for your prompt reply... would stripping the hair help?? Or would that just be more unhealthy chemicals added to make it worse??