My boyfriend has an enlarged prostate (psa17)he had surgery three months ago to shrink it (microwave)and his psa went down to 11but is now back up?

Irrelevant. The psa often goes up after any injury or inflammation to the prostate. This has no bearing on prostate cancer risk however.
Other conditions. Psa elevation are usually seen in cancer of prostate, but however other conditions like inflammation also will have elevated levels of psa, if persists your urologist may repeat the biopsy.Need to be followed by urologist.
PSA 17 TO 11. You did not say how old your boy friend is.Psa of 17 and enlarged prostate will make us think.Did he have biopsy of the prostate and was it positive or negative for prostate cancer.His psa is still 11, without double guessing the urologists who are treating him, he should discuss these questions from the urologist.He definitely needs if not already done biopsy and proper therapy based on that.