Like your surgeon, I would recommend waiting at least 3 months after stopping breast feeding before proceeding with any type of revision. From your photographs, in my opinion, a revision of the surgery with a mastopexy and repair of the side capsule (capsulorraphy). You might want to consider buttressing the cinching up of the lateral capsule with a piece of Strattice to insure that it does not stretch again. Good luck with your revision.
Revision breast surgery
From the photos you would need a full lift, not just implant revision. That should be address after you are fully done having kids.
Best Breast Operation for Me?
I am sorry to hear about your concerns after breast augmentation and subsequent pregnancy. Based on your photographs, it is likely that you will benefit from revisionary breast surgery which will likely involve breast lifting surgery as well. Best to wait until you have completed pregnancies before undergoing any additional surgery.
Best to communicate your concerns/goals directly with your plastic surgeon, preferably in front of a full-length mirror and with the help of goal photographs. Learn about the pros/cons/risks/complications associated with the revisionary breast surgery. You may find the attached link helpful to you as you learn more.