Welcome @Ella123,
This whole thing is full of so many decisions. Trusting your own instincts is the best way to go, although you will probably never be 100% sure you have made the right decision either way and that's normal.
I had a lumpectomy for 19mm stage 2 Tumour and re excision a week later as the margins were too close for their liking.
The decision for me was easy. The first words I said to my surgeon was I don't want a mastectomy unless there is no other choice. His reply "Ok, now we have something to work with" He didn't try to talk me out of it although I am sure for him it would have been easier as it was a shit of a thing to find.
We had to go searching for the breast tumour as 3 mammos and numerous u/sounds couldn't detect it. We knew it was there because the lymph node (that's where I found the initial lump) had already come back positive. MRI located it.
So I ended up with the lumpectomy, axillary clearance, chemo due to the node involvement and 30 rads.
I had no problems with the rads, did not suffer any fatigue and my skin held up well until the last 5 or 6 treatments and healed very well afterwards. The cosmetic outcome of the surgery is quite good and hardly noticeable to anybody but me.
The only after effects I have from rads (18 months on) is that if I am out in direct summer sun I can feel it burn a bit through my shirt.
All the best with your choice sweet. Trust yourself.
xoxoxo