The period when you finish your radiotherapy is very strange. You've had nearly 8 weeks of people fussing over you and treating you every day, and they usually really nice and it becomes quite a social occasion (maybe a bit less so during COVID).
Then everything stops. Where's everyone gone? Why have they stopped helping me?
Well, what's happened is that your radical treatment finished. It finished because they hope they've cured you. Yes, I know that's not a word we should use, but it takes a while for that so sink in - you were pre-treatment for months, and then having treatment for a couple of months, but now it's over - you're done! It takes a while for this to sink in to your mind, and it can be quite depressing thinking you've been left in limbo, until you realise.
However, Macmillan (and maybe other similar organisations) run courses specifically for this time. HOPE is one example, and I think it can be done as a half day course, or 6 shortened weekly sessions, and it's done with a handful of other patients in the same situation.
You usually get a 6 week and 12 week followup (PSA test before the 12 week one). These are your opportunity to feed back how you are, and request any followup services you need. If you think you could benefit from ED clinic or pump clinic, this is the time to ask. You won't get much feedback on how the treatment went, as that's generally not known until the hormone therapy finishes and testosterone returns.
It's worth keeping up with pelvic floor exercises - I stopped after the RT, but later noticed it had deteriorated, and started them up again (at a lesser level), and it very quickly improved again.