The risk in such a case is quite low..Condoms are highly effective in reducing the risk of HIV transmission and other STIs when used correctly and consistently. But there is still a small possibility, so consult a doctor.

It requires immediate visitation to a urologist. The cause of the disease may be injury, infection or testicular cancer. This underlying cause needs to be diagnosed by a medical practitioner 

Hi! If after the urination, you observe drops of semen, and you worry, do not; it is something that often happens in males. Typically, it happens because the residual semen might come out later. It is no biggie unless you are experiencing other symptoms such as pain or that burning sensation. 

More detailed history and tests like Uroflowmetry and Ultrasound with Post void residual measurement will give accurate diagnosis. If it’s BPH only and not improving with medicines then might need a surgical treatment. There could be other reasons like urethral stricture or high bladder neck which is also dealt surgically.

Masturbation andd night discharge are two separate physiological processes. While some individuals experience nocturnal emissions during their teenage years, not everyone will have them, and it is entirely normal.