I know it is not what you want to hear, but you are too young for steroids. Unless you have a medical condition, at 20, your test levels are already sky high. No need for steroids.
The lack of gains you are describing is called a plateau, and is very common. What I recommend is a change in your workout routine. With a new workout plan, you will bust through that plateau and continue making gains naturally.
You only have extremely high natural test levels for so long. Don't f*ck with them now, and risk messing them up for the rest of your life. Steroids will still be there in a couple of years when your natural levels start to decline. I wish I had the test levels that I had when I was 20.
I know that this is not what you wanted to hear, but believe me, it is good advice. I urge you to listen to it. Your body will thank me later. I have also given you this advice in a much more polite manner than I have seen it given out previously by others.
I also forgot to mention that if you are only 20, you are not allowed to post in this section. Read the rules, my friend. Good luck to you. I hope you make the right decision.