What Causes Pain In Abdomen And Lower Back ?

Hi there, I have been suffering from a pain in my stomach on the left hand side just down from my ribs. It is a dull ache, sometimes feels like the stitch. If the pain is not in my stomach it seem to move around to my lower back where it is like a dull ache. Can you think what it could be. I haven t sought medical advice as I thought it would just go away. I have had it for a month now. Sometimes having to go and lie down to get some relief. Thanks Barbara