Stress and what ifs are going to consume me

Hello all, as many I have been lurking around for some time and am just now posting. I would first like to say you are all amazing and it has been great to see how supportive everyone is here. I am posting in the hopes that if I finally let this all out maybe I can calm down a little. About a month ago I started getting random sharp pains in my left breast, it was nothing consistent and I just assumed I did something weird and it would go away. It didn't and in fact got worse and became constant, along with my entire left arm always tingling. I scheduled an appointment with my obgyn and she felt a pea size lump and scheduled me for a mammogram. I went to that appointment and they did the mammogram along with an ultrasound as well and found what the radiologist believes is a fibroadenoma. I believe she said it was 5cm, I still haven't seen the report so I am not sure. She wants to do an ultrasound guided biopsy, I now have that scheduled for next week. I feel like I am losing my mind. I am in pain (it's not always unbearable but it's always there) and my arm just feels odd, it's like it's asleep all the time. They don't think my arm is related to anything with my breast but it just seems weird to me that it didn't start until after everything with my breast. I guess I am not here to ask any questions really I just really needed to put this all out there. My husband is the only one who knows anything and refuses to believe that anything could be truly wrong. I can't help but to think the worst because that's what I do with everything unfortunately. I'm only 30, I have five kids and my youngest is just turning one this month. I feel like I am being ridiculous for worrying so much. It's honestly pretty sad just how many times I have cried the past few weeks. Thanks to anyone that has read this far.