Entire body stretching and shrinking

Hello, I'm trying to rig a character to move their head with my mine in my webcam, and most of it seems to work. The head stays attatched to the body, the arms and legs bend as they should due to the limb ik, But the problem is, when I raise and lower my head, instead of the body moving to accomadate it just stretches and shrinks, causing a warping that ruins the entire thing. Is there something I've tagged wrong? Ive looked for other posts or videos on how to fix this but none of it seems to address what im getting. Any help would be much appreciated