Do doctors take practice in testosterone injections?

I'm 19, and i'm pretty underdeveloped compared to my friends. I'm 6'2 have hair under my armpits, pubic hair, but it seems like I skipped some parts of puberty. Like my voice sometimes breaks, and I could probably pass as a prepubescent 14 year old, voice-wise... I also still look pretty young despite being really tall. Also, I can't grow a beard for the life of me, I haven't shaved a day in my life. I have a somewhat goatee, it's not a full fledged goatee, but it's not peach fuzz... would injecting me with more testosterone force me to undergo these changes?