What Causes Pain In The Left Shin?

I am a 17 year old dancer and for the past 3 months I have been experiencing pain in my left shin. About a month ago, my ankle started having some pain and stiffness. Now my knee has started paining me as well. It's a mild-moderate pain and rest and ice don't help. The pain is equal whether I am using my leg or just sitting/laying down. I haven't gone to a doctor because my parents don't think there is anything wrong.