Do I have congenital symmastia and did my over the muscle implant placement make it worse? (photos)

From what I can appreciate from your photos, your breasts simply do not have a large intermammary distance but there is no disconnection of the skin from the sternum that symmastia patients have. Placing an implant on top of the muscle likely just added volume to the breast and with that added volume your intermammary distance appears even more decreased. The skin over your sternum does not look disconnected from the underlying sternum though. Best Wishes!!

I don’t see significant symmastia in your pictures.
I think your biggest problem is related to the excessive skin redundancy.
Removing that much breast skin is inherently difficult and led to the outcomes you have.
I think most plastic surgeons would probably favor, subpectoral augmentation, but there’s nothing inherently wrong with placing the implants above the muscle.
Both techniques have their advantages and disadvantages.
Using excessively large implants is going to increase the chance of complications and need for revision surgery.
I think the size of your skin envelope is contributing and inherently limited the aesthetic potential outcome.
Compared to where you started I think your outcome is actually fairly typical or average.
Best,
Mats Hagstrom, MD