It's actually ok to sleep on whatever side that is comfortable for you. Just don't sleep on your tummy or your back, flat. I tried to sleep on my left but with terrible heartburn, it gets very uncomfortable even on any side so I will keep changing sides until I can sleep. Gets really uncomfortable when you're in your 3rd tri. You'll toss and turn until you get the right position. Sometimes I will sleep on my back but elevated with pillows. 1 mth pp today.
as long as your baby is healthy and happy inside your body, don't worry much abt the shape of your body, it will return to normal after delivery. (: