Medical marijuana questions and others... 10 points?

Ok... I live in Cali and have been going to the doctor for back pain for about 6 years and they found a bone out of order but re aligned but still hurts alot and I was wondering... Can I get a medical marijuana card and what is the law? ( age requirement , ECT .) and I also have minor arthritis and depression I hide except with my bro or when I drink to pass my pain.. Please don't hate and just answer this. Thanks