Do not pass off a bladder infection. The infection can worsen and cause complete urine obstruction.
The are no STD's, however this doesn't mean that you are completly out of the woods. Nonspecfic urethritis, for example, it can cause from watery to heavy discharge, itiching in uretha, Pain in the head of the penis, in urethra, in the testes, and groin.
The cause is often psychosomatic, however, antibiotics of various types are employed for treatment. You should discuss this issue with your Doctor, a referral to a Mental Health provider may be helpful.
Hope this answers your question!
REFERENCE(S)
1. WebMD, 2006.
Discharge from the penis