help me find this book about an autistic boy making a friend online

I remember reading a portion of this realistic fiction book years ago but forgot the name. It was about an autistic boy, i'm pretty sure the cover has a blue background I remember one scene, he was describing a flashback when his parents asked him if he loved his newborn sister and they were surprised when he said no. He was talking about how he can't find a reason to love her because she doesn't communicate, she can't help or do anything, etc. I believe the main plot was about him making a close friend online