Hello and thank you for posting, please do not feel silly.

I am sorry you are worried about how you are feeling and whether it is the cancer. But 10 weeks ago it was removed, with no sign that it had spread via your lymph node system so the likelihood of this pain being caused by the cancer is low. But, you have started a type of treatment that is well known for its side effects, so the likelihood of these pains being from Tamoxifen is higher.

Hormone therapies can take a while to get settled into the system, and many women have symptoms during this time, these often include joint pain and swelling.

This forum on the 'living with cancer' thread, and the Breast Cancer Now forum (from the UK's Breast Cancer charity) will have other women in a similar situation to you. It is sometimes good to hear from, or read about, others going through it too, to not feel alone so do have a look.

Taking some over-the-counter pain relief, gentle exercise, and taking each day while you are still healing mentally and physically should all help, but do also talk to your Breast Care Nurse (BCN) and explain how you are feeling.

Take care and if you want to talk it through with the nurses on the helpline it is freephone 0808 800 4040. Lines are open mon-fri 9-5. 

Sarah