Penis problem!

Im 25 and i recently went to a urologist because of a hard pea like bump on the under side of my penis.  there was pain, very uncomfortable and very swollen. The guy said he "thinks" its a skin infenction and put me on anitbiotics. around 2 weeks later no pain, no swelling, no hard lump but my penis is noticeably shrinking. It is losing girth and im freaking out. Theres also a new vein like thing in there. Please help, im going nuts