why does my spine stick out?

You do not have a *protruding spinal cord. If you did, you would be severely disabled with a fundamentally malformed spinal column. A bit like an impossibly extreme case of spina bifida (impossible as anyone born with a spine that severely deformed would either be a stillbirth or dead within hours).

The spinal cord is the main communications highway between the brain and the body: essentially it is a projection of the brain down through almost the centre of the body. It’s extensively protected by being located deep within the bones forming the spine and by running almost through the centre of the main body trunk.

Those bones, known collectively as vertebrae, have loads of muscle attachment points called vertebral (or spinal) processes. They can be very long in relation to the size of the individual vertebra they are part of. 

Those are what you’re seeing projecting from your back. On anyone who isn’t overweight it is totally normal to see them protruding below the skin, but individual genetic heritage also means that they’re more visually obvious on some people ( and less so on others).