Some labs will only go to a reading of <0.1 which would still be considered undetectable in that case.
We would want another PSMA pet scan if my husbands PSA started to rise (his is measured to <0.025) but we were told that this isn’t likely to happen until his psa reached 0.3.
I can understand the anxiety of waiting 3 months for another test, although like you say a big possibility of some benign cells causing it. Is it worth asking if you could have monthly tests for now? Possibly your consultant could write to your GP if easier to get them there….that’s what we do.
Best wishes
Elaine