Arm is showing when holding an item, and front of hair of skin shows in corners of screen

 I join any world and I hold an item. But my arm is still showing, I hold any item and this happens. It shows the item where it would be if the arm wasn't there, so it's just there with the arm. There's also another problem, I wear any skin and the hair is viewed in first person. The hair is shown around at the top, left and right of the screen. So all I can actually see is what's in front of me! It appears in creative and survival worlds.