Fair enough - about the mammogram I mean. Sounds perfectly sensible - I had a mastectomy so missed that particular kind of anxiety. Certainly my underarm (axillary clearance) took a long time to feel like it was even mine let alone normal!
Your body and mind need time to absorb all this stuff. Everything happens very fast after diagnosis but it doesn’t all land. Anxiety, aches and pains, anxiety about the aches and pains, funny sensations, anxiety about the funny sensations are all par for the course!
I saw a counsellor for a few weeks after my third potentially lifelong side effect - I wasn’t depressed or particularly anxious, just a bit confused about how I was supposed to be and to behave. Among a huge amount of useful skills she imparted (still using them eight years later) was to spend at least 20 minutes each day in nature doing nothing. Just breathing, feeling the sun or wind on your face, looking but as far as possible not thinking. Can possibly be done while walking (also a really good thing to do). The purpose is to engage with simply being alive. Our anxiety is all about dying. Focusing on living helps regain some balance.
The panic is understandable - I discovered a lump under my other arm while still on chemo. Long story short, utterly benign unrelated tumour, possibly been there for years. We think EVERYTHING is cancer, for a while. We need to take every opportunity to practice the other stuff - laughing, enjoying, relaxing - before we lose the knack! Be kind to yourself, this is all very new and raw, and at a difficult time. It will improve. Best wishes.