Hi K2. I'm in a similar situation to you with an increase in PSA to 13 over the 12 months to Dec 2010. Prior to that it was around 2 for 5 years. Put on antibiotics (originally noroxin (a fluoroquinolone like cipro) but because of severe tendinitis had to go onto a less powerful antibiotic) for 4 weeks - but it continued to climb to 19. Examined by a urologist, who specialises in prostate cancer, last week - he said could not feel any lumps but one side felt as thought it was infected (a bit more spongy). He went on to say that the only to sort this out (as not decreased by antibiotic) is biopsy which I will be having in 2 weeks.
From my reading, the PSA from either acute or chronic prostatitis can rise dramatically, well into double figures like we have. The free PSA will also be low and resemble the same free/total levels you can get with prostate cancer. However, while the PSA levels with an infection tend to jump around a bit, the levels with PCa tend to show a steady rise over time. I think an infection leads to increased leakage of the PSA out of the prostate into the blood stream.
With regard to your groin and lower abdominal pain I (not a Dr) do not think that is inconsistent with an infection - do a Google search on prostatitis symptoms. If it is an infection, then some can be quite difficult to remove - but usually of limited impact on your quality of life. If you can see a urologist soon than that sounds a good move to at least get some progress for you - I imagine he would consider three options - another PSA, DRE and / or a biopsy.
All the best.