GP's dismissing my complaints about a breast problem for nearly 4 years

No you are not alone but perhaps a letter to all the GPs involved telling your story will heightened their awareness of possible cancer and in future they will refer to a breast surgeon earlier. So glad you persisted and finally got a diagnosis.

We can't go back and change the past but hopefully can assist in changing the future. Right now though you need your energy on the now, your treatment recovery and acceptance of your changed self. We are here to help where we can. Kath x