Breast Cancer Self Examination Part 3: When Lying Down

Doing a breast self-exam lying down is the second half of the “feel your breast” part. When you lie down, your breast tissue spreads over your chest wall, making certain areas more accessible than when you’re standing up. Even with lying down, there is a right position to do the exam in: if you’re checking your right breast, place a pillow below your right shoulder and your right arm below your head. The method of examining is the same as examining in the shower: using your finger pads, and in a circular pattern.

Source: 

Breastcancer.org