Here's a quote from the National Cancer Institute:
Free versus attached PSA: PSA circulates in the blood in two forms: Free or attached to a protein molecule. The free PSA test is more often used for men who have higher PSA values. Free PSA may help tell what kind of prostate problem a man has. With benign prostate conditions (such as BPH), there is more free PSA, while cancer produces more of the attached form. If a manís attached PSA level is high but his free PSA level is not, the presence of cancer is more likely. In this case, more testing, such as a prostate biopsy, may be done. Researchers are exploring additional ways of measuring PSA and comparing these measurements to determine whether cancer is present.
According to that, "the free PSA test is more often used for me who have higher
Prostate-Specific Antigen (PSA) is released from prostate cells, and some other cells as well, when they are irritated in any way, and you have a lot of irritation going on. In light of two recent negative biopsies in the last few years, I think you are wise in your decision to consider other options first.