Help guess this breed of dog?

Pink
This is my puppy I adopted from the shelter. I adopted him when he was about 3-4 months old. He is 1 year now and we still can't tell what kind of dog he is & we are very much dog people (know our breeds). I think he is a lab/pit mix but he is very lanky & is already measuring taller than the average male pitbull... Maybe American bulldog mix instead? Anyone?