Dearpjaz
Waiting is one of the most difficult times but while you are experiencing shock and disbelief, it may actually help to remember that breast cancer is hardly uncommon (sadly), that treatment has improved over the years and an early diagnosis is a terrific start.
It’s also too easy, particularly in the absence of firm details, to imagine one horrible outcome over another. Try as hard as you can to only worry about what you know. The world is full of things that might happen, we would all be paralysed into total inaction if we acted on every possible fear. Keep ‘helpful’ people who want to tell you about their aunt’s illness or the website they found, at bay. They may mean well but can do real harm. Remember that reactions to treatment vary wildly - I had six months of chemo (much more developed cancer) and never as much as felt remotely sick. Ditto fatigue and brain fog.
It will help when you know what your treatment is - a breast care nurse may help a lot too, talk to your surgeon or GP. Do whatever it takes to calm your mind and heart in the meantime. Walk in fresh air, breathe deeply, listen to music, whatever. Best wishes.