I agree with the previous poster, If you are growing your hair out from scratch, the hairs on the top of your head will take longer to get to the back thatn the hair already back there. This results in a huge gap in the hair, between the top and bottom, and lots of layers in between. My hair looks like this, as I have not had it evened off yet, since I started growing it out a year and 8 months ago. Some of it is probably also layered from some breakage.
You haven't said whether or not your hair is natural, but I am going to guess it is from the description of the layers. As far as the thinning of the ends, part of this may be due to breakage. But much of it is probably more of the extreme layering. If you put the 2 together, you will end up with sections of hair that have a huge variety of lengths, even in a small section. It may seem like your ends are thin, when those thin ends are the longer hairs. If you are relaxed, I would say the thin ends were probably due to the weakening of the hair shaft because of the chemicals.
The last question for me would be, is your goal to have long hair? If it is not that much of a concern for you, feel free to layer your hair, or more gradually grow your layers out. If your goal is long hair, you will need to have your hair blunt cut, for optimum length, and retention of hair. Refer to the link I posted a page back, that says, A "link to a HUGE amount of hair info..." I have heard it somewhere else before, but it further substantiates on that link, that you need to have your hair blunt cut if you want to grow it-keep it, long.
The info there says the hair has life cycles, and when you have hair in layers, even bangs, your hair starts shedding, to even the hair out. Hence, cut it one length, to help prevent unnecessary hair loss and massive shedding. Read more info there to get the complete story. After reading it, I will be evening off my hair sooner than I planned to. HTH
