Lower Back Pain

Hello, I am a 20 year old ballet dancer.  I have an extremely flexible back and have never before experienced back pain (even when other girls in the class were hurting from using their back muscles, I was always fine) but for the past few months, I've found that my lower back is in agony after class.  It feels almost as if my spine is compressed - like there is a weight bearing down upon it -  and I find myself wishing someone could just take it out of my back and stretch it out for me.  The pain comes and goes, getting better when I have a day off from dance and feeling the worst after a long night of classes.  Does anybody know where this "compression" feeling is coming from and whether I should see a doctor or chiropractor?  Dancers are notorious for just letting go of pain, just chalking it up to unavoidable soreness, but I can't seem to get rid of this.