Thanks for answering. Yes, I have had blood drawn, and a urine test. Results were that I didn't have any of the infectious diseases that they tested for.
Sorry, I should have made it clearer: I really feel as though this must have something to do with my injury (see my "straddle injury" post below). But the urologist was disinclined to believe that. According to him, pain and swelling from an injury of this type "should" disappear within a few hours, or else there should have been some more drastic damage that would have hospitalized me long ago.