It's food intolerance...
It's all about diet with IBS. My husband has it, not nearly as bad as you mention but the diahreah (spelling?) was ruining his life. We have stopped that with an oat porridge (add a tablespoon of golden Linseeds) every morning, calms and fills the stomach. If he misses the porridge he has to run to the toilet all day.
Definately look into Candida and parasites. Avoid any foods that might upset you, wheat, dairy and refined sugar. My husband drinks a glass of milk and in 10 minutes his bowels open up - he thinks this is great, when it's really about the fact that his stomach cant tolerate it. Get tested with Kenesiology to find out which foods to avoid.
Peppermint oil capsules (time release) for cramps and neausea.
Enzymes to assist digestion.
Probiotics.
There are a lot of herbs that soothe, like licorice and willow, slippery elm, cant remember the others but do a search.