I wouldn't be panicking too much with a PSA figure of 13.7.
Having started at 135, mine was brought down to 0.4 through intensive chemo and radiotherapy but then (probably as expected) started to climb a bit over time. When it got up to 8.4, my medication was switched, in the hope that it would then go back down again.
However the most recent figure (a couple of months ago) was 27. So I've been on 'double dose' medication (with both injections and tablets) for the past two months. I've got a CT scan on Thursday, and then a blood test next week, before a telephone consultation with the consultant in a fortnight's time. Apart from some tiredness and fairly minor lymphoedema though, I've got no real symptoms from my prostate cancer. (Even my peeing is fairly normal).
So, Barry, if I'm still here 3½ years after being diagnosed with late-stage (4a), highly-aggressive (9, on a scale that goes up to 10) prostate cancer, I don't think that you need to be booking the crematorium for yourself just yet ;-)
PSA counts vary naturally across time anyway, with even something as simple as recent sexual activity (including masturbation) known to push it higher.
If you're still concerned anyway though, push for further testing.