Nippy, I agree with what Citty says. Please do be gentle with yourself; it sounds as though you are expecting yourself to be all things to all people when no-one can be. I know first hand how extremely difficult it is to cope with your own stresses whilst your parents go downhill at the end of their lives, and how so many people don't appear to understand the fatigue that this causes. And, you have the psychological stress of cancer on top of that, never mind the physical effects.
Are you assigned to a Breast Care Nurse in your hospital, or a Macmillan nurse? You could ask about getting emotional and psychological support; your GP might be able to help. The phone number for Macmillan Cancer Support is 0808 808 00 00, 9.00 am to 8.00 pm, Mon - Fri.
I'm also wondering whether complementary therapies might help. Is there a Cancer Support Centre attached to your hospital? If not, Macmillan might be able to advise you on finding suitable help. Relaxation techniques, massage, reflexology can all help to reduce muscle tension which itself contributes to fatigue.
As has been mentioned on other threads, we all have to put ourselves first at times and look for help in looking after ourselves.
I do hope you find suitable support and are feeling better soon.
Nippy, I think you're being very hard on yourself! With all that you've had going on this year it's a wonder your not flat out on the floor never mind fatigued. I think when we go through something like this it's easy to blame "the tablets" (and I'm absolutely not dismissing side effects) because that is something we can control whereas most life events, like the loss of your father and your mother's illness, we can't and we've already lost so much control when we were diagnosed. It might be worth seeing if you can speak to your oncologist anyway or maybe your GP? I don't know what age you are, but could you now be menopausal? I'm sorry about your father and hope you feel better soon.