Harry

It sounds like you have the friend intestinal flora out of balance like a yeast infection. I think you need to do something to get it back rebalanced. Like eating a good brand of yogurt or kefir and take a probiotic supplement several times daily.
I like and use Enzymatic Therapy "Pearls" , PB-8 by Nutrition Now also I like Stonyfield Farm yogurt and Helious --kefir.
You may even have to go on an Anti Candida diet to get the friendly bacteria back in balance. YEAST thrives alot on sugar/ carbs so you have will have to reduce these foods and drinks.
Nausea and fatique are not normally associated with IBS. But too much diarrhea of course can make you weak and fatiqued.

These symptoms you have -- could be connected to some things like a round of antibiotics, too much salty, sugary or spicy foods. I get the bloating even with alcohol.---- They all can just mess up your digestive system.

I wish you well---Harry