Capsular contracture from sleeping on stomach? 1.5 years post-op silicone, under muscle

It sounds like you may have experienced a tear in the capsule around the implant or a tear of the pectoralis major muscle. Either can cause bleeding (hematoma) which would explain the initial swelling. Typically, bruising follows. But, sometimes the capsule contains the hematoma and no bruising is visible.
Hematoma is a risk factor for capsular contracture. I recommend consulting with your plastic surgeon for an in person evaluation. I would investigate with an ultra sound to determine the next steps.

Dear RSMember027721,
I understand your concern. However, without a proper assessment, it would be difficult to determine what went wrong. It is best that you visit your plastic surgeon for further assessment or ask for a second opinion. Only after a thorough examination, you can get proper recommendations and advice.
Daniel Barrett, MD
Certified, American Board of Plastic Surgery
Member, American Society of Plastic Surgery
Member, American Society of Aesthetic Plastic Surgery