According to Mayo Clinic, sleeping on your stomach places a strain on your back and spine. This is because the middle of your body is where most of your weight is. This makes it difficult to maintain a neutral spine position when you are sleeping.
Stress on the spine increases stress on the rest of your structure. Additionally, since the spine is a pipeline for your nerves, spinal stress can cause pain just about anywhere in your body. You can also experience tingling and numbness, as if parts of you have “fallen asleep†(while the rest of you is uncomfortable and wide awake)