Your case is a classic example of the benefit of ultrasensitive testing. Many here oppose it, preferring the one decimal place result, but ultrasensitive can give up to an 18 month advance warning re. what is going on.
For example, your first two PSA results (standard test) post surgery (Oct '14, Apr '15) were <0.1 (less than 0.1) which is a good result with the standard test and what you want to see.
Your next three results were done at the ultrasensive level,
(6/23/15 - 0.023) (1/13/16 - 0.064) (5/20/16 - 0.086) which, had they been reported using the standard result, would also have been <0 .1, falsely indicating all was still going well.
But the ultrasensitive results indicate a steadily rising PSA from at least June 2015 through to May 2016 and this is confirmed by your latest reading (of 0.132 in Dec 2016)
PSA doubling time is a proxy for the speed of tumour growth. As the cells divide they double in number and therefore double in PSA ouitput. Slow doubling time is what you want to see for it means the tumour is growing relatively slowly.
Your doubling time seems to be about
8-9 months which is fairly slow. At that rate your PSA should hit the probable additional therapy trigger figure of 0.2 about
May 2017. (which may be what your doctor is looking at)
Here is a doubling time calculator:www.doubling-time.com/compute-PSA-doubling-time.php
And here is some interesting reading:/www.pcf.org/c/radiation-therapy-following-prostatectomy/