Penis :: Constant Tingling On Glans

For about a year now I've had this incredibly annoying sensation inside my penis around the top area going down to maybe just below the glans. It's almost as if I feel that I need to pee even though my bladder feels completely empty. It never goes away. I've had my self checked. First time a doctor said that there was a "little bit of an infection", then he gave me antibiotics. I came back after the symptoms hadn't gone away. Sometimes it stings very slightly when i urinate but not painfully. The doctor said the infection was gone in the urine test. I then went to a urethral doctor and they performed a cystoscopy but didn't find anything wrong. after that I went to std clinic where they did tests for the typical stds but didn't find anything and they didn't have a clue of what it could be. I really can't relax with it, but it's definitely not psychological. i have also noticed since i got this sensation i can last anywhere near as long during sex or masturbation, so badly that I don't even bother, but I wouldn't care if i could just get rid of this sensation/irritation/ TINGLING.

Oh and one thing is that the std clinic they said it could be nonspecific urethritis if the std tests came back negative which they did. so they gave me zithromax 1g(1 day) and cipro for 5 days, it did not eliminate this feeling. So they concluded that it wasn't nonspecific urethritis because NSU would have disappeared with the zithromax.

I've searched the internet and I can't find anything relevant, and was hoping that maybe you guys know something. I'm 21 years old.

if anyone could help me find a solution or what I have and remove this feeling I would be so incredibly thankful, id even pay a damn reward (that's how sick and tired I am of this).