Welcome! I am sure you don’t want to be here but it’s a friendly place and people are happy to share their experiences and tips for getting through it all. It’s worth remembering that cancer is a collective noun! All of us have our own variations and differences, what one experiences doesn’t necessarily apply to another. But we do all know what it’s like and empathy is an important factor.
The mastectomy is usually pretty straightforward and often not very painful. Fluid drains are a bit of a pest and time with them can vary a lot. I didn’t have radiation so can’t advise but chemo is a bit of an unknown until you start. I was lucky, had few reactions and worked throughout, others have a much tougher time. You might want to plan for any hair loss. Many find it easier to shave their head, or cut their hair very short, to minimise the falling out process (usually a couple of weeks after starting chemo). Your scalp
may start feeling uncomfortable too, very common. I chose to wear a wig but many get creative with scarves or just embrace the skin!
I did see a counsellor for a couple couple of months and found it invaluable. Everyone is, quite rightly, focussing on your physical issues but the mental ones (not necessarily depression but often confusion, what should I be doing/not doing, what’s happening to the life I planned?) are often significant. I found an experienced other (not a friend or partner) was terrific in helping me clear my thoughts, and get on a new (and better) way of thinking. Your doctor may provide a referral (worth getting a regular GP for the duration) or a Breast Care nurse. I didn’t have one of the latter - some find them wonderful, others not so much - but the senior oncology sister where I had chemo was super smart and very helpful.
Try not to overload yourself at the start - this stuff takes some getting used to. Day by day is the way to get through. Let others know what assistance you want and need and also what you don’t need!! Even those near and dear sometimes have absolutely no idea what to do and need a little guidance from you!
Best wishes.