Just wanted to wish you well.
I happen to be the exact same bra size as you and, to be honest, I've always been really happy to have small breasts.  Much more comfortable, especially for sport.  The figure of a fashion model!

I'm sure you are doing the right thing - health must be the priority.

There is a helpful thread here... www.cancerresearchuk.org/.../breast-total-duct-excision-i-hope-this-helps-someone

Very best wishes for the best outcome.

In 2013 I had discharge and clear mammograms and was recommended a duct removal which I had. Not wishing to alarm you, but they found a small lump of DCIS which they removed and I had radiotherapy. It was all handled very well, quickly, calmly and smoothly, so even if they do find something it may likely be something treatable and may not require the removal of the breast.  They may find nothing.

But from an aesthetic perspective my breast was slightly smaller than the other one but not massively visibly at all and the scar was very neat and almost disappeared within a few years. You would have to look very carefully at both my breasts to notice any difference. I am slightly larger than you naturally but still very small chested! I hope that helps, good luck with it all.

I've had multiple surgeries to remove ducts for duct exctasia the last one was a breast reduction removing 500 mg each side, so they could remove as many ducts as possible finally my breasts have settled down. That was 16/ years ago the ducts felt like pieces of wire l have had cysts and infections so many antibiotics. I hope your surgery goes well and solves your problems. 
susie