Brief history . (Posted on here so I don't keep whining on other threads)
Been a vegetarian since 14yo (I'm now 49). thought I was ok health/dietwise until I got extreme pain both sides of abdomen.
After tests (scan,colonoscopy,) I had a gallstone (removed gallbladder last year) and diverticular disease. (Extreme loose bowel, bloating,cramp)
So, through some trial and error. Cheddar cheese can leave me in agony ( improved since the gallbladder removed) but can't eat much.My cholesterol levels have improved since I cut down.
Some Quorn leaves me with painful bloat.
I don't eat butter (don't like it).
Lactose free milk made no difference
I used to drink a 300ml bottle of orange juice (stopped now)
So - been adviced to try low FODMAP and had to make some changes .
I've removed pasta,bread,pastry,biscuits. Now GF bread,GF pasta, ricecake. I'm going to try cornchips
Removed all dairy (even though FODMAP allows hard cheddar,lactose free,) in favour of soya milk , almond milk and soya yoghurt.
I've had no fruit, but tried some pomegranate juice. I'll try banana and grapes.
I'm ok with Quorn fillets it was the Best of British Quorn sausage that caused the problems.
For protein, I can eat eggs.
Should I ask my GPs for a Dietician referall? Should I do this diet for say , 3 months then ask?
I do feel better (a bit) less bloating pain I've noticed (but that could be mind over matter)
Oh, and no milk chocolate. 
Got a bar of Bournville as an Extra Special treat to have an odd square. Joy.
Really meh because I thought I was eating quite healthy (before all this happened) but obviously , not.