Is this overly swollen or a uniboob? (Photo)

It does not look like symmastia according to your pictures but you should consult with your surgeon to be sure. Symmastia is a condition which can occur when the implants are too close together. Patients often refer to this as a “uniboob.” This can occur for the same reasons as displacement, but in this case the pocket(s) is/are too far towards the center.Correction of this problem may involve using different implants such as textured, a smaller size, or a smaller base and placing the implants in a new pocket. On occasion, this may require surgery in more than one stage to allow the tissues to heal and then place the implants. If the implants have been placed above the muscle, converting them under the muscle frequently will help and, again, the use of a dermal substitute may be required for additional support if the tissues are thin. The techniques of capsulorrhaphy and neopectoral pockets may apply here as well.

Thank you for your question and photograph.  Swelling is normal after any surgery, but should be steadily improving.  It is difficult to tell from a picture if the skin overlying your breast bone has been lifted, leading to a unbid look.  I would be in touch with your operative surgeon, who will better be able to answer your questions about swelling (ruling out other possible causes) and the skin between your breast.

I am sorry to hear about your concerns after breast augmentation surgery. Online consultants will not be able to predict, whether or not the skin "tenting" will dissipate as swelling completely resolves. As you can imagine, much will depend on whether your skin was somewhat elevated in the area prior to surgery, how/where the breast implants pockets were dissected, and what size of breast implants were utilized.  Best to communicate your concerns directly with your plastic surgeon who will always be your best resource for accurate diagnosis, advice, and/or meaningful reassurance. Best wishes for an outcome that you will be pleased with long-term.