Fibrocystic breasts or cancer? (27f)

Ok I just want to start off and say that 27 isn’t too young for BC. I’ve seen several women my age or younger on TikTok sharing their stories and it’s spooked me out more but also makes me feel not alone on this. Anyway… for a year now I’ve had a lump in my upper middle quadrant. I found it before my period because it was sore. It’s pretty big. Atleast an inch. It’s hard sometimes and sometimes it’s not. Got an ultrasound on it and they didn’t see anything alarming. The results came back “no mass found” I started digging around where my armpit is and I felt a few lumps there. Like on the upper outer quadrant. Same breast. Got another ultrasound. Came back fine but suggested I get general surgery in my chart but when I called to schedule they said they just do that for everyone as a precaution and my results were fine? I lost insurance right after this and wasn’t able to get in for any more testing. Now it feels like the lump is sore. I’ve read so many stories of women that have these symptoms that ended up having positive breast cancer and I’m terrified. Never heard of them getting clear ultrasounds though but I’m scared that the tech just missed it. I’m going in for a mammogram finally on the 7th and I’m sooo terrified it’s going to be too far gone. I’ve had arm pain when I’m on my period and the lump is more sore. Sometimes it’s sore, sometimes it isn’t. Last period it was sore on both breasts on the upper outer quadrant but normally it’s just the lumpy side that causes issues. No family history besides my aunt who is 63. To the doctors that’s not super alarming because she’s not a close close relative and she’s much older. I keep crying about it especially watching TikTok’s because the symptoms are so relatable but yet they are so close to fibrocystic breasts. The lumps are all moveable. They aren’t hard or soft really. More firm. The only one that’s ever hurt is the big one in the middle. There’s another big one right next to it as well. Like a perfect oval shape. The first one I found really feels like a giant ball of tissue. It’s hard to even distinguish the shape because it’s not really a shape?