your result looks very nice. But, if you do not feel comfortable with this result then you need to interview several different surgeons to see the opinions and the choices for your improvement. your before pictures would be very helpful to see the beginning tissue. breast enlargement has certain restrictions directly related to your beginning shape and contour and fullness and symmetry..... certainly, going smaller is possible. every choice you make, there are pros and cons, there is NO perfect choice or operation.
You can get your records from you surgeon and see if he marked them down. Best of luck moving forward.
You can try and measure the original BW and it shouldn't be too complicated. You would benefit from downsizing and going with a lower profile based on your concerns. Go to a consult and see if you feel better afterwards. I think you will with a revision.
Your preoperative photos or imaging may help in determining your pre-surgery breast dimensions. At this point, that may be helpful, but is certainly not necessary for planning an implant exchange since your pre-augmentation dimensions may have been altered by the surgery.
A lower profile implant will decrease the upper pole roundness and lessen the cleavage especially if you decrease the volume slightly.
Your breast asymmetry seems to be due more to sagging in your left breast than something caused by the implants. If this is a concern, a breast lift will improve the symmetry.
You really will need an in-person examination to assess the characteristics of your tissue and discuss your specific goals to determine the best option to get you as close to your ideal as possible.
I'm not sure you can find out your original BWD at this point but you can look at your "before" pictures and discuss your concerns with your surgeon to see if there is any room for improvement.
If your surgeon has a Vectra 3-D imaging platform, and has saved your preoperative photographs, then it's quite easy to go back and visualize the measurements of your base width diameter prior to implant surgery. If not, and only two-dimensional photographs are available, it may be difficult if not impossible unless the photograph was taken with a standardized size object like a ruler is visible in the photo so you can translate that to the base width of the breast. If not, then you have to guess based on what's in there how many millimeters you need to go smaller in order to give you the look that you think you want. Good luck with your secondary surgery.