I Have Severe Pain In My Lower Back And Under

I have severe pain in my lower back and under my right rib cage. 3 months and getting worse. I've lost lots of weight. Have been unable to eat a full meal and about half hour after I get stomach pain... I now have a strange pulsating in my side and round the front... It is worse when sitting... I have been on transform & patacetamol to calm the pain... But if I don't take painkillers its unbeatable..
Also have lots of itching on my torso!! Not sure who to see as I am always at doctor...