High psa after surgery

My PSA scores for past 10 yrs hovered around 3, with it spiking this year to 15. Biopsy showed cancer, with gleason of 9 (4+5), with about 25% of left affected. Bone scan, pelv ic scan and lung xray were clear pre surgery. I had surgery(prostatecomy) at end of July and had his first PSA about three weeks ago, with it indicating it dropped only 5 pts. I had another PSA done about 3 weeks with an increase of 2 to 3 tenths (could be within margin of error I suspect). 2nd bone scan done about 2 weeks ago clear as well. I will be having a prostascint scan this Tues and Wed. I find it hard to wrap our heads around this because: gland was small when removed, doctor said he cut wide when removing it and all margins were clear, 11 lymph nodes removed and all were clear as well. Gleason 9 is concerning. Cancer also found in one seminal vesical. Any thoughts welcome.