Unprotected Oral Sex With Different Partners, Constant Burning Urination, Warmness Over Penis, Tingling In Anus. Any Thoughts?

I m a 23 year old boy. On September 22, 2012 and October 8,2012 respectively, I had two separate occasions of having unprotected oral sex with 2 separate girls from the same massage parlour. It was one of the most idiotic things that I ve ever done in my life and I regret doing those. In line with that, I felt weird sensations in my penis tip which felt that I had to urinate a lot. Also felt that my penis was unusually hot. There was no yellow or white discharge from my penis In line with that, I went to the hospital to get my swab test and urinalysis done on October 23,2012. Doctors informed me that they found nothing from my gram stain that would indicate any infection and that my urinalysis was clear. For the next 4-5 weeks, I had no symptoms, except for a tingling in my anus . Then, around 5 days ago, I am feeling the burning effect during urination . There is still no discharge, but it got me thinking. Any thoughts?