My breasts flatten out when I lay on my back? (Photos)

It is normal for big breasts to fall to the side when a woman lies down. That is just gravity. Nothing to worry about.

If your breast implants are falling off your chest and into your armpits while on your back, that's one thing. That doesn't appear to be the case from your photos. From your photos, it appears as if you're experiencing what women with naturally fuller/bigger breasts go through everyday. It is normal for breasts with any type of mass to them to fall to the sides when laying on the back. This is also a normal sequelae of getting larger implants. The ribcage has a rounded shape, not flat, so breasts slide along the curvature of the ribcage. If your implanted breasts stayed pointing straight up to sky while on your back (like Barbie breasts), it would likely be a result of capsular contracture. Breasts that look like that are often referred to as "bolt-ons" due to their unnatural, hardened appearance. Capsular contraction is when scar tissue forms in the chest cavity and tightens around the implants making the breast hard and unnatural looking. Furthermore, it appears as if your native breasts were more laterally positioned with a big space in the middle before the implants came into the picture. Breast augmentation does not change the breast "footprint" on your chest. A low breast will stay low. A wide space will stay wide. A woman with a lot of space between her breasts will only get that "cleavage" with the help of a bra/bikini top.