After surgery it may take time to get used to how your body feels. Positioning can help this. Often side lying using pillows for support is beneficial. Place a pillow between your legs with your knees bent. You can also place pillows behind you to give you support, between your knees, under your top arm and of course a good full pillow under your head. For some people pregnancy style pillows can be beneficial as they offer a lot of comfort and support.
Some people prefer to lay on their backs. If this is the case a pillow just at the crease of your buttocks can help tilt your pelvis to improve comfort in your lower back. Some patients also like a couple of pillows under their head and shoulders if in this position. Gradually in time you should reduce the support to being one light pillow under your head if laying on your back.
Ultimately comfort is most important and it is whatever works best for you.