@Tammy9
It’s a shock, particularly when you feel you have looked after yourself and are fit and apparently healthy. Unfortunately breast cancer can occur in fit people with no family history of cancer.
Hard as if may be, now is the time to take one step at a time. Deal with the surgery before making decisions about the next step. Get an understanding of the implications (good or bad) of your pathology results.
The treatment plan may sound hellish but it may not be as bad as you think. Chemo is capricious and unpredictable but, that said, some people find it manageable and nowhere near as bad as they feared (I am one of them). Remember that any course of treatment can be stopped - stopping if it is too difficult to continue may be an alternative strategy to never trying a treatment at all.
We would all understand the dilemma - up to now you feel perfectly well, but treatment may make you feel very ill! It seems utterly mad. But step by step many find a strength they didn’t know they had and a determination to lick this thing they never wanted.
I hope you have the support of family and friends. It’s a part of your life you could do without but it’s not the whole story. The purpose of treatment is to free you from cancer - which is worth the best shot you can give. Very best wishes.