I had really bad health anxiety about a year and a half ago, like to the point I couldn't function. All I did was cry. And watch sad movies. In bed. Or think about my death. And how my kids would react to my death. And how much I wanted to live for them. And how much I wanted to live for me. It was an atrocious feedback loop that I couldn't escape. All of it related to the long wait for biopsy results on a breast lump, then persisted through an almost immediate after the breast lump scare a few mole biopsies. I had never had health anxiety before. But, damn. I really let the fear of what the doctor was going to find control me during that long-a$$ wait. I basically checked out of life for a while.
Even though I was a basketcase and my husband lost patience with me (and maybe a little bit of respect longterm, lol), I have come to the conclusion that that tiny breakdown was exactly what I needed to go through to become stronger. I am 42, and I am going to continue to find things on my body. So, while I am far from perfect at controlling my intrusive thoughts about disease and death, I do better now at managing fears when symptoms crop up. I also still look for things, but not like I used to. I don't go over in my mind every toxin I have been exposed to and its link to cancer like I used to. I don't google as much as I used to.
I don't know where you are in your history with HA, but maybe you can just give yourself permission to think the absolute worst-- but put a time limit on it. I have an active imagination and would let myself think out the most horrifying things- like having stage 4 cancer, wasting away to nothing in front of my kids, not being able to speak to them in my final days, stuff like that. And, you know what? Thinking those thoughts helped me realize that is the worst case scenario with cancer, not everyone's experience with it, so why in the world was I imagining it would go down like that for me? I don't know if this approach would help everybody, but I feel like it helped me.
I know you are afraid of cancer right now. The chances that you have cancer are very slim. There are so many explanations for breast and armpit lumpiness that are not cancer. Googling creates a misleading picture. Are you getting tested? Maybe just allow yourself some time to wallow in your worst thoughts but then promise to release it once you get good news, which I know you will!!!!