Right off the bat, I want you to read this other thread. It probably appliles to you:
http://www.medhelp.org/forums/STD/messages/4153.html
'The next day I felt a tingling/mildly itchy feeling at the tip of my penis.' Strong proof against any STD. No infection can cause symptoms less than 36-48 hr after exposure. Good likelihood of anxiety magnifying normal body sensations.
'1 gram of azythromycin followed by 500mg amoxicillin 3x daily for 7 days.' After that treatment, no chance of an STD that could cause such symptoms.
'2 gram dose of metronidazole, followed by 500mg metronidazole twice daily for 3 days.' Ditto.
'Some days I feel it, some days I don't.' Strong evidence against infection as the cause.
'I have no discharge and no pain during urination.' More evidence of same.
Answers to your specific questions. 1) Yup. 2) Yes. 3) Yes. 4) No. Forget it. You don't have anything except nerves.
Good luck--- HHH, MD