Unresolved problem

About 4 months ago, i had unprotected sex with a girl.  The next morning i woke up and my penis was very irritated and had some discoloration and has been that way since.  At certain points it has been dry and flaky but the head of my penis has consistently been discolored and wrinkled, which it was not before.  It has been like this since the sex and the discoloration has slightly changed but has always remained.  Also, when i masturbate, my penis is more sore and irritated afterwards. I have been to both my general doctor and a urologist who both say that they do not see anything because there are no lesions.  I have been tested for all stds and have recently been using hydrocortisone cream, which my urologist recommended, but it has done very little.  I have also tried using monistat incase i had a male yeast infection, but that did nothing as well.  I am running out of ideas and it is becoming increasingly frustrating that nobody seems to have an answer for me.  Any ideas?