First, your hair is very pretty let me tell you. Second, I feel for you, for a long time I had the same problem (I still have it! you can see in my profile picture how the right part is longer and thicker than the left part). I thought I could fix the problem by cutting the curls in the longer part to even it out, however, after a few month other curls will grow longer than the rest and it will look uneven again.
So what I did was: accept it! I just don't mess with it anymore. I accepted the fact that my hair does its own thing and grew to like it the way it is. When someone tells me your hair is uneven in the back I tell them: I know! Isn't it funny how it's just hair but it has its own character and it does its own thing! To me my hair is like my child, I accept it even with the things that bothers me so much about it. There are many things I could think of that would make my daughter the perfect child, however she is perfect with all the things that are "unperfect" in her.
I know it's hard to do and it takes a while (I went through bad periods of anger towards my hair) but if you hang in there you may grow to accept it and please don't cut it, you may think that we're only telling you this to support you but I am 100% honest, your hair is gorgeous, it's full of life and thick and just beautiful!
A Mediterranean 3b lady
In love with my curls, love love love
CG since Nov/07

Co-Wash: VO5, Tresemme naturals, Fructis naturals
Cond: Nature's Gate conditioners
Stylers: Lotions made at home with coconut oil, honey, AVG, vegetable glycerin, OO, and EO.
Gel: LA Looks sports gel for high humidity days.

Hair goal: Waist length healthy curls