esselamu alejkum I have a question regarding islamic way of "sleeping". I read one must sleep on right side some websites talk like left is bad evil ect. Is that true first of all and how can it be? I sleep on L and R and back side, sometimes my back hurts and left side just feels better to fall asleep. I have slept on my belly too when I had some issues? Why would GOD care about that I don't understand the logic behind it. Also body constantly shifts during sleep because if you sleep constantly on now side you would be in pain/discomfort. What do you know about that? Thank you for your answer.
Alaikumassalam wa rahmatullah,
The Prophet 
preferred using the right side in most things, and from that the manners of things like sleeping is derived. This is just a recommendation. I know some Muslims make a big deal of it, but in my view, as someone who has read Ṣaḥīḥ al-Bukhārī and Muslim and other hadith sources, I can tell you that it is a very minor issue. Personally I sleep on whatever side I prefer. In fact I often sleep on my left side because the right side gives me stomach trouble.
As for sleeping on the stomach, please see this answer: Sleeping on the stomach is not clearly forbidden or disliked in Islam