Suggest Treatment For Pain In Lower Left Side Of Abdomen Right Below Ribs

Hi, I have been having pain in my lower left side of my stomach right below my ribs for a couple weeks I have been to the gastro doctor and they said nothing is wrong with me. I still get the pain mostly when I lay down on that side. I did the same tonight and now the pain wont go away and seems to be getting worse. I have been very light headed for a couple days mostly all day not feeling my self what could be going on?