What Causes Chronic Left Sided Abdominal Pain?

ok i have had this left side gnawing pain for a while which has progressedto a dull pain ,its been ongoing for about 3 yrs: ive just dealt withit bc ive had alllthe tests done andthey just sAID I HAD MEGACOLON : anyways the last week ihave had ahot burning sensation that comes directly down my face from the bridge of my nose down to my top lip and mouth but the sensation only occurs on the left side of my face therehas been increased lower back pain lately as well but ive been managning it wiht asa and anacin which seemsto get me straightend out to walk