Back Sleeper
Simply put, these people sleep on their back, flat as a board. This position is great for your organs, because it gives them room to spread out. and it is also great for people with lower back pain. However, if you are prone to snoring, this position will not be your friend as it increases/enhances snoring! Use a flat pillow in this position so your spine and neck can stay aligned. If you really want to protect your back, sleep with a pillow or two under your knees, although this isn’t extremely necessary.
Side Sleeper
Congratulations, you are positioning yourself in the most beneficial sleeping style. Sleeping on your side allows your spine to be in its natural state and provides a comfortable position for your neck that doesn’t add unnecessary pain or pressure. Make sure you have a good and supportive pillow so your head doesn’t sink below the natural line of your spine and cause any strain. It is also recommended that you sleep with a pillow in front of you to rest your arms on so you do not round out your shoulders too much. Make sure you have a soft mattress or even a pillow under your shoulder so you do not put too much pressure on the side you are sleeping on.
Stomach Sleepers
Welcome to the club. Guess what? We sleep in the worst position possible. Why you ask? Sleeping on your stomach not only crushes your organs from all the pressure, but by keeping your body straight and turning your head 90 degrees to the side, which I assume you all do as to not suffocate in your pillow, you put unnecessary pressure on your neck and you sleep in an awkward position for your spine. Guess who else isn’t a fan of your stomach-sleeping habit? Your girls! Yup, they probably don’t like being crushed for such an extended period of time. However, if you are not a well-endowed collegiette™ this might not be as big of an issue.
I know hearing your favorite position is harmful to you may not be the best news, especially when it is just so comfortable and relaxing, but it is probably in your best interest to slowly transition to a side or back sleeper. No matter how comfy sleeping on your stomach may be, do your body and spine a favor and assume the correct position!
Source: http://www.fitsugar.com/Pros-Cons-Sleeping-Your-Side-Back-Stomach-14571804