I agree, at 20, you should not have hit a hard plateau yet. How long have you been training for? You should have lots of your own 20yr old testosterone floating around! hahaha. Up your cals, up your workload and intensity and change your program around frequently. If you are really maxing out, I would suggest doing a good newbie cycle, perhaps a number of short cycles like the type that Nelson Montana has mentioned over the course of a year.
If you dont want to try that route, you could go with a simple 8 week cycle of test/eq/dbol. I would run the test at 250/wk, EQ at 200/wk, dbol at 30mgs/day for the first 4 weeks. You could also run some winny tabs or anavar for the remaining 4 weeks at 30 mgs/day for better results. A lot of people will say to up your doses of test to 500/wk, and EQ to 400/wk, but if this is your first cycle and you want to play it safe I would go with the first option. However you WILL gain more with the second option, and should be alright regarding sides, provided you do your homework and read up on protective measures and post-cycle treatment. Good luck.
Mavy