Do I have lateral implant displacement? Does this get worse over time? (photos)

An examination is needed to be certain, but your photos do suggest that you do have some lateral displacement. Wearing underwire bras can be helpful, and wearing a good support bra when exercising is needed. If this displacement bothers you, you can have this fixed surgically.

Hi and welcome to our forum!
From your photos, I note normal relatively symmetric breasts with no evidence of sag. I do not see evidence of lateral drift.
Normal breasts fall laterally to the side when resting on your back. Excessive lateral displacement with exposure of the ribcage between the sternum and the implant would be an example of lateral drift. This phenomenon may also be associated with pain. It may be due to the presence of a large implant, error in pocket creation, or weakened connective tissue of the chest wall.
Best wishes...

Dear B456,
I understand your concern. However, without a proper assessment, it would be difficult to determine what went wrong. It is best that you visit your plastic surgeon for further assessment or ask for a second opinion. Only after a thorough examination, you can get proper recommendations and advice.
Daniel Barrett, MD
Certified, American Board of Plastic Surgery
Member, American Society of Plastic Surgery
Member, American Society of Aesthetic Plastic Surgery