Suggest Treatment For Pain In The Lower Pelvic Area

Hi- I've had pain in my lower left pelvic area for over a year now. It comes and goes and sometimes at night if i move suddenly using my abdominal muscles, it seems to pull or tighten and be very painful. I also get a dull pain on my right side as well.There is also pain in my tailbone area and i wonder if it[s all caused from the same thing? Any thoughts on what it might be?