How close together are your retightenings? I think that you should space them further apart and then that might help you get the thickness you want. The next thing to consider is do you know what interlocking pattern your loctician is doing? She might be using a 4 pt. rotation and if you want your locks to be thicker she should be using a 2 pt. rotation. Since I know you like neat hair, you will probably be happier with a 3 pt. rotation.
I think your hair looks good, you just have to stay patient and let it do its thing. But I will also say that you can probably achieve the ideal thickness you want if you combined waiting longer in between retightenings with a 2 or 3 pt. rotation interlocking pattern.
If all else fails, you can combine all of your locks...but the way your patience is set up, I already know you ain't about that life.