Sorry to see that your husbands PSA is starting to rise again.
My husband sounds a little similar to yours in that he won’t think anything is related to the cancer whereas I assume everything is 🤦🏻♀️ he also thinks the same way with regards chemo.
He could potentially be worried about the rise himself which could maybe cause some weight loss and fatigue (this happened to my OH when first diagnosed) also back pain could be something else. Hopefully with his numbers still being very low then these symptoms are not related, fingers crossed you can get some answers soon though. My mind runs away with me sometimes and I constantly fear the worst, the only positive with that is its usually never as bad as I have feared.
Wishing you both all the very best x