Might be pilaris keratosis. It's when your body is producing too much protein in your skin. The bumps are not whiteheads, or blackheads, they're more like under the skin bumps, that when squeezed out pops a fleshy, white type of plug. Sorry for being so graphic. My ex had this on the back of his arms, and on his upper back.

It could also be hormonal, since the jawline and neck seem to be where hormonally imbalanced people break out the most often. I've never heard of it happening all over the neck when hormonal though.