I am 15 years old. About five feet and eleven inches, I shave about once or twice a month, but only because the hairs are blonde and I have armpit hair legs hair and a solid amount of pubes, bit my penia has shown no signs of puberty and I have yet to ejaculate. Also, although I am pretty tall I have never had a real growth spurt an I am expected to grow some more.
You are definitely in puberty if you are shaving and have armpit and pubic hair.
Have you ever had a wet dream? "Nocturnal emissions" are a way for your body to release "old" semen that has built up. It's normal. Usually you'd wake up with sticky shorts - often after an erotic dream.
Have you tried masturbation? What happens?
4-5" would be about average for a 15 year old.
Remember, don't compare yourself to others. Everyone develops at different rates/times.