I don't want to rain on your parade or anything, but if you have only been in the gym for 6 months, you SHOULD NOT be doing
steroids. You are 20 yrs old and you have enough natural test in you to make some good gains, my friend. And BELIEVE ME, 6 months in the gym isn't enough.
My advice is to give it some time. Train hard for awhile and eat right and let yourself build a good muscle base....
Peace.