Did you try eating a lot of soluble/insoluble/prebiotic fiber (feed your bacteria with fos/inulin/oat bran/apple pectin...), drinking lot of water and exercise?
Also "Bifidobacterium animalis DN173010" from Danon has very posstive studies:
"Researchers for Danone have chosen to use BL RegularisTM in Activia® for its beneficial properties pertaining to the digestive system. BL RegularisTM has been shown to play a role in intestinal transit. Slow intestinal transit, principally due to bad dietary habits and stress, is a source of discomfort (bloating, heaviness, aches)."