I think you have a nice result, unfortnately people get numbess especially when implants are combined with lifts, the asymmetry is part of the deal its impossible to make someone 100%
It's very difficult to tell based on your photos. You need to be examined in person by a BC PS. If you want a second opinion, see a BC PS in your area.
The differences in your breast could be related to healing though there can also be a natural asymmetry in the breast envelope. Excercise and further settling may be the best course for now.
Looking at your photographs, the left inframammary fold appears lower (photo labeled "difference in size"). A physical exam would be necessary to determine the reason for your asymmetry. I would advise scheduling a follow-up visit with your plastic surgeon, so you can be examined, discuss your concerns and determine what treatment (if any) is needed.
Sub-muscular implants shape are defined by the muscle. The muscle wants to be down on the chest wall and is stretched with larger implants. There is also a connection between the muscle and the breast that we try to shape by doing a mastopexy or lift. A Binelli donut Mastopexy only tightens around the nipple and tends to flatten the anterior breast. Implants do settle with time, but I do a lot of secondary revisions due to the muscle by changing the plane to sub-fascial where the implant defines the shape and softness of the breast, not the muscle. Patients will typically need a full mastopexy to shape the breast into more of a conical shape if the skin and breast tissue is loose.
Very difficult to give you good advice online. Your photographs, as well as a description of “feels empty” suggests asymmetry of the breast implants in the breast “envelopes”. This asymmetric may be related to differential breast implant “settling” and may explain why your plastic surgeon has advised continued “exercises”. I would suggest that you follow his/her advice and see him/her and follow-up to rule out other potential causes of breast asymmetry, such as early breast implant encapsulation.