Is this lateral displacement? One of my implants is already settling further round toward my armpit. (Photos)

I am sorry to hear about/see the problems you are having after breast augmentation surgery. I think your concerns are appropriate; your breast implants do seem to sit quite low on your chest wall, consistent with breast implant displacement ("bottoming out”).

Although some “falling to these sides” of breast implants is quite normal when you lie down, if this occurs “excessively”, it may be a concern to patients.  This phenomenon is called lateral displacement of the breast implant;  it may be of concern from the visual and the discomfort standpoints. Surgical correction is an option.

Generally, the lateral breast implant displacement and bottoming out can be corrected using an internal suture technique, decreasing the size of the pockets and moving the implants toward the midline.    In my practice, I use  a 2 layered suture technique (capsulorraphy) to close off the space inferiorly (correcting bottoming out) and laterally (correcting lateral displacement).

Generally, signs of breast implant bottoming out include: 
1. Breast implant "sits" too low on the chest wall.
2.  Excessive palpability or visibility of the breast implant along the lower breast pole.
3.  Nipple/areola complex seems to be sitting relatively high, because the breast implants have settled too low. 
4. Discomfort along the lower breast pole (secondary to pressure from the underlying implant).
5. Relative paucity of upper pole breast implant volume compared to lower pole volume.
6. Increased visibility of a infra mammary fold scar (higher on the breast mound).

I think you will likely benefit from revisionary breast surgery which will likely involve capsulorraphy (internal suture repair). Sometimes, depending mainly on the patient's history and physical examination, I will also use additional supportive materials such as acellular dermal matrix or biosynthetic mesh. This procedure serves to reconstruct the lower poles of the breasts and prevent migration of the breast implants too far inferiorly.  Any associated issues with positioning of nipple/areola complexes and visibility of the inframmammary fold scars should improve with this operation.

 I hope this helps.

Thank you for including photos! Your NAC position suggests that your implants are 'bottoming out' or sliding down too far on your chest wall.  Lateral displacement is harder to assess without an in-person exam as your breasts were fairly widely spaced prior to surgery - some surgeons will manipulate the pocket position to minimize this while others will follow your natural anatomy. Have your surgeon assess your implant mobility and they should be able to tell what's going on with your pocket. Best of luck!