You are right, a PSMA PET scan is really what is needed right now. Since this came on so quick, they will probably find metastasis that they can zap with SBRT radiation and your PSA will go down again.

Being on both drugs at this time means that you have probably now become castrate resistant. Happened to me six years ago while just on ADT. At that time, ARPI drugs worked for me.

Depending on what they find with the pet scan they may want to do Pluvicto or Chemo, But that would be unusual for such a short term rise in PSA. More likely, they will find something to zap.

Wish you the best. I know my combo of ADT and ARPI will not last forever, so many of us are just waiting our time. I have heard of some positive clinical trials going on right now for people in this situation.