Hello. I am almost in your situation. I had mine on 23rd Nov 2018. Below are a few results.

Jan 2019: 0.11
April 2019: 0.11
June 2019: 0.09
August 2019: 0.12
December 2019: 0.12
April 2020: 0.12
August 2020: 0.11
October 2020: 0.17
December 2020: 0.15
February 10th 2021: 0.18
MARCH 24th 2021: 0.13

I became very alarmed when it shot up to 0.18 and my doctor referred me back to the urologist who explained that they can see some ACTIVITY because of the rise and fall. He then referred me to a radiologist who has requested PSMA PET/CT scan. I am due for it on 7th April.
I will suggest that you contact your urologist may be for a PSMA PET/CT scan. I do not know what pertains in your country but here I am paying 31USD for the PET scan. In Norway we are all covered with a national insurance.

Before the last scan I stopped some medications – allopurinol and crestor as I was told that the former can raise psa level and the latter can reduce the level thus giving false values. No sexual activity for 3 days before I went for the text. I am not sure these might have contributed to the sharp decline.

I was also advised a high psa level does not necessarily mean prostate cancer has returned as they could be normal cancer cells. However, I do not want taking chances, so I monitored my psa every 3 months instead of the 6 months that was recommended.

I wish you the best.