Many of us will readily understand the tension of waiting - some people find that the worst experience of all. Your doctors are doing the right thing, however terrifying it may be. If it is cancer, then the sooner you know, the sooner you can have treatment and the higher the chances of recovering. Remember that bit about recovery!!
I didn't find a lump, my breast suddenly became rather red and tender (not worsening pain). When I did find a rather painful lump under my arm on the other side of the affected breast it was a schwannoma (non-malignant). So hard to tell at this stage. Friday's tests should give a good indication, so best I can suggest is hold on to your sanity any way you can till then and try and keep as positive about finding the cause (and then the treatment) as possible. Very best wishes for Friday.