Hello Jodyanne,
To answer your question succinctly the PS is not at fault, because there is no apparent deviation from what would be considered a normal result, at least by the photographs posted. Additionally, you more than likely signed off on the myriad of complications listed in your preoperative consent forms, including implant dropout/malposition. Having said that, I am not saying that you should be happy with your result.
Without actually knowing the conversations you might have had with your PS prior to surgery, you probably got just what you asked for, based on statistics and what I know from personal experience. Unfortunately, most plastic surgeons do not stress strongly enough how important it is to choose an implant that is appropriately sized for the patient's anatomy. Additionally, larger implants are less predictable than smaller implants with regards to healing and the potential for complications like yours. Similarly, higher profile implants are less predictable than lower profile implants. You are an example of someone with implants that are too big for your chestwall/breast width and have suffered dropout and malposition into your armpits.
To be blunt, you cannot have that much augmentation. It doesn't matter that your friend/sister/cousin got the same size (or bigger) implants and she is doing fine. You won't. Get used to the idea that the breasts you want in terms of shape and position on your body need to be smaller.
Revision surgery is more complicated than primary breast augmentation, and should be performed by highly experienced revision breast surgeons. Certification by the American Board of Plastic Surgery and membership in the American Society for Aesthetic Plastic Surgery are also important as well.
Best of luck!