My hair is growing the same way, and I was wondering what to do about it. I am currently in the Hide Your Hair Challenge, so I am keeping it in protected styles for 6 months. As I transition from one style to the next I think I'll do some trimming. I don't want to get to a length that I love only to find that the very back of my hair hasn't caught up. I would rather do mini trims now then have to do a major cut later.
The back of my hair has always grown more slowly than the rest, and I am trying to be patient. The protective styling should make this slow growing phase less painful, but it's still frustrating to gain obvious length in some areas and slow growth in others.