Hi and welcome, I'm sorry to hear of your diagnosis, but good to hear treatment is working, I went through the same treatment and also had discomfort in the testicles, it's due to the hormone therapy stopping you producing testosterone, of which 95% comes from the testes, as a result they will shrink and this is the reason for the discomfort, but always talk to your team about any concerns. A  3 or 6 monthly PSA test is the norm for less aggressive prostate cancer, with a more aggressive variant regular scans are often, but not always needed. Best wishes.

Eddie