Hi Adrian, orgasm and cycling can raise the PSA for about 48 hours afterwards but it is thought to be a difference of less than 10% so at very low numbers is rather irrelevant. Having a DRE raises the PSA by more than that.
My husband was always reminded of this but the doctor didn't say 'don't do these things' - he was more interested in consistency & wanted John to try to do the same things as much as possible. So if he went out on his bike this time but not last time, we have to try to remember that and not panic if there is a tiny rise in the PSA as it is probably temporary.
To be fair to your doctors, your zapped prostate no longer produces ejaculate so sex is unlikely to make a huge difference to your test results!