Breast Sagged 3 Year After Breast Augmentation?

Sagging can be caused by inadequate support (provided by a bra), larger implants, and the general aging process. You may have also had some sagging before your breast augmentation as well, which should have been addressed at that time. I am sorry to hear about your experience but it sounds like a lift may be the most suitable option for you at this point. 

Hello! Thank you for your question! The mastopexy (breast lift) procedure raises the breast, which ultimately provides a more
youthful and perky breasts. This is done by
removing the extra loose skin and rearranging the surrounding breast
tissue in order to reshape and support the newly formed breast. At
the same time, the nipple-areolar complex (NAC) is raised to the ideal position above the fold beneath your breast (the
inframammary fold) as well as being placed at the most projecting portion. Oftentimes with age or following pregnancy, the NAC
becomes widened and enlarged. This may be reduced in size during the
breast lift procedure.
It is common for the breast to lose its firmness and uplifted appearance over
time, which is also accentuated with age, pregnancy/breast feeding,
weight gain/loss, and gravity. This results in breast ptosis, or
sagging of the breast, with a “deflated” appearance. Women seek the
mastopexy procedure to regain the previous youthful appearance of her
breasts and women report increased confidence, self-esteem, and
femininity once achieving this desired shape and fullness. Breast lifts
may or may not be performed with implants – the implant would add
increased size but also greater fullness in the upper pole of the
breasts which creates more cleavage.I would discuss your
concerns with your plastic surgeon. Increased size of the implants as
well as laxity of the native skin do cause increased stretching
inferiorly. Revisions certainly may be considered - allow your surgeon
to examine and evaluate you and then go over which procedure(s), if any,
will be the right one for you. Best wishes for a terrific result!

This is difficult to explain and Ihave no specific answer for why you would observe rapid swelling and ptosis in a milld breast enlargement