I suffer from similar butit tends to happen over night causing me to itch very badly, its causing me to have very restless nights and disturbing my sleep.
It started after a 2 month period of switching to vegetarian eaiting, on and off. I thought it was the beans, and I stopped them for three weeks, and I still had the uncontrollable gas, and anal leakage. Now its been brought to my attention that soy causes gastro problems, for a number of reasons ( Dr Mercola, "soy is not a health food" youtube - look it up). One thing I started eating that was new was Tofu, and soy milk. Plenty of it. Perhaps this is what is causing it. Ill lay off that for a wile and see what happens.