What is the reason for a weak erection in a 23-year-old?

Hi doctor,

I am a 23-year-old male, not married. I weigh 174 pounds and I am 5'7" tall. I have been experiencing weak erections for the past five months. However, l have not experienced any common symptoms of prostate cancer. Two days ago, l started feeling an acute pain in one of the blood vessels that led to the right testis. I had to take Ibuprofen to ease the pain, and it eased. I started examining my semen with the naked eye and saw that it contained very tiny and very few black particles in it. Today l examined my semen again, and it was as normal as it used to be, no tiny black particles were seen. However, my issue is about weak erections. I am still experiencing them to this day. I have not visited a doctor yet concerning the issue of not having erections, l only tried a dysfunction treatment tablet (Kamagra), but there was not any change till today. I have never had sexual intercourse all my life. I only masturbate regularly. I once experienced pain in the same blood vessel when l was twelve years old, and it lasted for only 24 hours. But l have never experienced difficulties in having erections.