Forget steroids, you need to eat correctly for the next few yrs and you will put weight/mass on, if your not eating right its pointless, it takes longer than a couple of months.
Taking steroids shuts your own test production down so when you come off steroids you wont have any testosterone and you need to restart it up again, if your young and your system hasnt fully developed you can cause yourself a load of problems, low testosterone: erection problems, mood swings,depression, fat gain,muscle loss, anger issues,emotional and many many more what you dont want to be having when your own testosterone is at its highest it will ever be, so dont shut your own system down use what you have instead of creating problems when your not even eating right.
http://forums.steroid.com/showthread.php?t=367187