I have a very shy girl, almost considered a spook. I've had her for almost three years and she has come around but is not the affectionate dog that my others are. She runs if I try to take a picture, she absolutely hates if I sit on the couch and she is there, she will immediatley leave the room, she hates crowds and shakes like a leaf if made to endure it. That tail of hers can almost lay flat on her stomach when she is really nervous. I had to come to terms with myself and realize that she doesn't have to be the outgoing dog that my others are. That she is who she is and we just let her be. I love her but she is one dog who you truly earn affection from. Her best friend in the entire house is our lab. What is really funny about this dog, her brother (same parentage but two separate breedings) raised at the same farm, was the complete opposite of her. He was confident and funny, sweet and loving. He never met a stranger in his life.
I wanted to also just give you a small piece of advice someone gave me a long time ago. With shy dogs I don't pet their heads, imagine if someone came at you with a large hand and patted your head. It's a bit obtrusive and scares some dogs. I always go for petting them under their chins. This is less obtrusive and Chesney may be more apt to come to you more often.