Well either your coaches are retarded or you mis-read them. You do not need and shouldn't use steroids at this time. If you want to get stronger and more muscular start lifting, eating, and reading on how to do so. Steroids are only a tool and even if you were older (19 is far to young) you do not have enough knowledge of training, or else you would have already realized this.
Ask your coaches what they really meant, if they say you should use, find different coaches. I am a MMA fan and I train (MMA)recreationally, but evwen I haven't maxed out my natural potential (5'9" 216 bp 330 squat 525 dl 500) therefore I won't juice (yet). I am learning everything I can and when I feel I have maxed my genetic potential I will be ready if I so decide it is necessary.