20 year old in pain:
first of all you need to rest your back and be patient. Back problems take a wile to heal. Exercise daily with easy exercises for example:
stretches - arm - leg - bun - abs
exercises...Just a few minutes each
take some good supportive supplements (e.G. I found one that really helps me, it is called sport.... Dexlen.Glycostore.Com/go/sport )
i know that when you are 20 your are anxious to keep on training but, and I can not emphasis that enough - it will take time.
I feel with you, because I pinched a nerve in my lumbar section and ever since I have a weak back, unless I follow the advise I gave above.
Hey, on the other hand, you may want to do some mental training as well (you do that when you compete right?) think about your back being all healed up and you are back doing your thing.
Good luck and good health - hope you achieve it soon.