Thank you for your question. A personal exam and consultation is always best.
That said I suggest waiting 6 months or preferably a year after finish breast-feeding before you have breast augmentation surgery. It takes time for the breast gland to return to a normal state after breast-feeding. If you have breast augmentation too early many of the glands are still producing milk, and have not atrophied or reduced in size. You want the gland to be in its final state before surgery. If you have breast augmentation while the gland is still enlarged and it reduces in size later this may affect your result.
Be sure to consult a plastic surgeon who is certified by the American Board of Plastic Surgery, experienced in your procedure, and who has an excellent reputation in your community.