Can a single person suffer from urethritis (std)? My urologist told me this in my case?

Proabably yes... Remember: despite medical advance, all medical care today is still based on indirect evidence resulting from continual collection and analysis of available experience. Furthermore, we're constantly battling an invisible war against all bacteria, virus, and fungus inside or outside of our body, and we survive if our defense ability is strong enough; many persons around are std-carriers. S0, maybe..