Possible STI/STD

I am a virgin at the age of 13 I want to find out what i have.

I have no past medical issues relating to this.

Another bit of information is that I masturbate frequently, maybe 1 time every 2 days.

The so called infection is located on the head of my penis, it doesn't hurt but look like a rash, no itching or other symptoms.

Furthermore it looks like read spots but have a rash going through the outside of it.

I cant grasp what i should do so i am looking for help.