Hi there. I read all of your comments with interest as I also have the brain fog, fatigue and aches and pains - but I did not have chemo. I had surgery, radiation therapy and endocrine therapy (ongoing) for Stage 2 Grade 2 BC. The physiotherapist said radiotherapy has a long term (permanent) effect in that your immune system is constantly trying to repair the "damage", but it can't. That is a cause of fatigue in itself.
The Tamoxifen side effects were dramatic - due to such a drastic and sudden drop in estrogen and progesterone, then the Zoladex injections (ongoing) and Letrozole combo had me feeling like I was at least 80 years old (I'm 55). However - I currently feel much less fatigued and have far fewer aches and pains after switching to Aromasin. I'm also on an antidepressant, Escitalopram, which helps too.
The oncologist said fighting the aches and pains all day is what made me so fatigued. The switch has improved my symptoms. Long may that last!!! Maybe a switching to a different endocrine therapy drug will help you guys too. I hope so. All the best. Lxxx