I'm so sorry you're dealing with this.
Do you have a family history of breast cancer?
The NHS don't usually do genetic testing unless someone is particularly young, has bilateral disease or has a strong family history.
However IF worst case it is breast cancer, you can absolutely advocate for mastectomy on the affected side plus contralateral risk reducing mastectomy, rather than just a lumpectomy. This often (but not always) avoids radiotherapy.
I had 7 affected relatives, young ages, bilateral disease, one ovarian, and I fought tooth and nail throughout my twenties for risk reducing mastectomies which I was finally grudgingly given at 29.
When genetic testing did become available, I learned I was negative, however I am incredibly thankful that I got it done, as I had large heavy breasts and the psychological trauma of having watched it rip through my family wouldn't have been erased by a negative test.
This has been tremendously freeing for me psychologically, and whilst it is not quite the same IF you have already developed a cancer, if this is early stage with no spread and you were to get both breasts removed, the physical and psychological benefits of the procedure going forward would be of almost the same value as a prophylactic surgery.
That was my cousin's situation, she had it on one side, fought for mastectomy rather than lumpectomy - you have more leverage with a diagnosis than someone seeking preventative surgery - then she fought for the other removed, which she was initially denied but stood her ground and eventually got it. The pathology showed she had also had an undetected cancer on that side too.
She now lives breast free and cancer free as well, and that was about 15 years ago.
Please try not to worry excessively whilst waiting for results. IF it is breast cancer, it is highly treatable now, and the main thing is it has been caught.
If you have daughters or sisters and cannot get genetic testing on the NHS, you can obtain this privately if you want. The cost now is a few hundred pounds, when it first came to market it was thousands.