Oh did you bring back memories. I'm seven years out, from surgery, chemo and radiation and
still on hormone blockers but I sure remember where you are right now. I too had no family history of any cancer much less breast cancer. I sort of assumed too...
First of all, even if you had history of cancer in your family, (mother, aunt or sister) there is only a small chance that you would get it too. While there is a gene (BRCA) that can predispose some women to breast cancer but they are most frequently Jews whose ancestors came from Northern Europe. Even if you're Jewish you might not have it. Even if you're not Jewish, they will test you for it. It's just a blood test. It isn't as genetic as we usually think.
You should research. Now this is my personal opinion, but I would recommend that you get a second opinion, not just of the cancer but of the course of treatment. It might mean traveling to a major cancer center or maybe Mayo Clinic. Some centers like Dana-Farber in Boston do second opinions online. https://www.dana-farber.org/appointments-second-opinions/second-opinion-program Your records and scans may have to go there, but you don't.
At best, you will know that your doctors' opinions are the same as at one of the major cancer center. Then you'll always have peace of mind that their course of action is exactly what you would have gotten at a major cancer center or the Mayo Clinic.
On the other hand they might notice something your doctors didn't or know some new treatment and you'd have an option you didn't know about. I wish I had gotten a second opinion. There was a different surgery that I could have had that might have had a better outcome.
Now, I hope I haven't made you more anxious. Don't forget your PCP. He or she knows you better than your cancer care team at this point. If you're feeling really anxious you should make an appointment with your PCP or PA. He or She might prescribe something to help your anxiety. But he/she will also understand that you need emotional support. He or she will review the pathology report with you. My PCP gave me extra time in an appointment and let me cry and scream. PCPs get it. You're not their first cancer patient.
You need to be good to yourself right now. If there is a place you like to go, maybe a park or a lake or the Ocean (I have no idea where you live). Maybe it is your place of worship. Just try to center yourself. Go there. Treat yourself to something special. If you like tiramisu or chocolate ice cream get it. If you have Diabetes, don't do that. 🙂 Make a special meal for yourself. Get your nails done. Go out with friends.
Don't try to second guess the whole thing at once. Everything in cancer treatment is one step at a time and everything will be explained to you. You'll be given tons of literature.
I used to say I am not battling cancer. I'm just showing up. I'm letting the doctors battle cancer. They have the expertise. You don't have to know everything.

As for your body betraying you that is going to take a long time. You're going to feel a sense of betrayal in different ways over a period of time. While you're going through it, you'll think you've gone down that rabbit's hole. But it gets better with time. You can't make it go fast. You are beginning a new life. You have your pre-cancer life and you are going to find you will have a post cancer life.
I didn't know about Mayo Clinic Connect until after my treatment. You're at least one step ahead of where I was. There are other support groups too. Check out SHARE Cancer Support. There is also an exercise program for people who have had cancer and/or are over 50. It's called Moving for Life. Some of the classes are by Zoom. It is gentle exercises. I took t'ai chi by Zoom through AARP. I found the American Cancer Society was very supportive. They too have peer support. You're not alone. You won't be alone through this. Ask your family and/or friends for support. They don't have a clue at this point of what to do for you. If you need someone to accompany you for appointments that can be very helpful just make sure that person isn't an anxiety driven person. You are the only one allowed to be anxiety driven right now. You want to assign jobs to calmer relatives and friends. When I needed a ride I didn't need someone driving and swearing at other drivers or worrying out loud about traffic or parking. You can assign your more anxiety prone friends to do things like running errands for you. Every job is important. I had a young friend who lived over 1.000 miles from me. She wanted to help. I appointed her my Public Affairs person. I sent her a list of everyone I wanted informed after surgery. I sent her their email addresses. Then I gave her email address to my boyfriend who would be at the hospital. When I came out of surgery he contacted my young friend on the other side of the country, and she sent out an e-mail that I had gotten out of surgery and was doing well. Get people involved. If you have a place of worship let them know at least let the pastor or imam or rabbi know. Members may be able to provide you with meals or do basic chores for you or they may add you to their prayers. People want to help you but you need to let them know how.
I can't tell you you're going to be okay. For awhile you're not going to feel okay. Right now, it's surreal isn't it? I can tell you cancer and cancer treatment is temporary. Your life has changed but it will get easier.

Write. Keep a journal, or a blog if you want. Remember don't define yourself by cancer. If you like to bake, bake. If you like to sew or do needlework do it or garden. If you like to play tennis or basketball, whatever, do it. You are more than cancer.