I don't know what black/purple lumps on the scrotum signify. That description doesn't remind me of anything, sexually-transmitted or otherwise (unless you're scratching bumps, which you should stop if you are.) In order to find out what this is, you will need to show them to a doctor. If you don't have insurance, you will need to pay for one visit. Many important things in life have costs and are not covered by insurance. I think this is one of them.
Best.
Dr. Rockoff
http://pg.photos.yahoo.com/ph/rudy6157/my_photos
Dr. Rockoff