From someone who has IBS and 2 years experience from having nothing but HELL I can give you the following advice:
Don't guess. If you want to know what's going on in your colon, get a DNA based stool test and have them check for everything: good bacteria, bad bacteria, parasites, yeast, inflammation levels etc.
Cost is about $400 to 500.
You would think that insurance companies would pay for something like this, instead of $1,000s of CAT scans, etc. But nope!