Congratulations on the clear margins. You have much to stay positive about. I know the feeling about the post surgery upgrade in Gleason score. My biopsy went from a Gleason 6 to a post-op pathology of Gleason 7 (3+4). My surgeon told me not to be discouraged at all - clear margins and lymph nodes are the biggie, and that although the cancer was a little more aggressive than what the biopsy showed, and although nothing is certain, it was "unlikely" that any cells remained. The upgrade in the Gleason score just verified my decision to have the prostate removed.
I had my first post surgery PSA test done one month after surgery, and was worried that there would still be some residual PSA in my system. If the results did not show "undetectable" I was prepared to request a second test. However, I scored a big fat zero and have been pulling them ever since.
Good luck with the first post surgery PSA