Avocado Grown from Pit Stopped Growing?

i have grown an avocado plant from the stone in the fruit. Once I planted it, it grew really quickly for some time, and then just stopped. I moved it into a better sun position and it grew some more. It's still in the same spot, but it hasn't visibly grown for months now, not even sprouting new leaves. It still looks healthy. Its presently about a foot tall. Its an indoor plant, also. What's going on? Do I have a plant that's afraid to grow or something? =)

By Kelly