I sleep on my right & left side....mainly left tho.
I bought this big long body pillow thing called a snoogle from toys r us. It is specially designed for pg & BF women. U can coil it up so u can sit propped up in bed or uncoil it. It curls at the top so it supports ur neck & also curls at the end which u place between ur legs. Its kinda like spooning something really really comfy & then when bubs is born u can use it to help with BFing.
I defently recomend getting something like this or a body pillow. U will use it heaps as ur pg progresses. I haven't slept so well for ages.....DF even steals it off me sometimes & uses it!