Do I Have Congenital Symmastia?

Your pictures demonstrate the presence of a mild congenital symmastia. This condition occurs when the breast tissue merges across the midline. In some cases, this may give the appearance of a large single breast.Cases of mild congenital symmastia don't usually require surgical treatment. This condition is well tolerated and is almost considered a variant of normal.If you're concerned about this problem, it's reasonable to consult a board certified plastic surgeon. This surgeon should be able to discuss this condition and the available options for treatment. In some cases, breast augmentation or liposuction may have a role. In your particular case, it's probably reasonable to do nothing and accept what most people would consider to be a relatively attractive breast. 

Thank you for the question. 
Unfortunately, without direct examination it is difficult to give you precise advice but it looks like you may have congenital symmastia.  I have found that treatment of congenital symmastia can be challenging. Sometimes patients with “congenital” symmastia  benefit from liposuction surgery of the area between the breasts ( over the sternum);  whether or not you are a candidate for this procedure will depend on your physical examination.
You may find in person consultation with well experienced board-certified plastic surgeons to be helpful to you.
Best wishes.

It appears you do have a symmastia. I agree with some of the other surgeons that implants may make this worse. I also agree that you have a very nice shape and size to your breasts and would likely not recommend you alter them in any way.