I used to get a lot of stomach ache and the gp diagnosed IBS. I tend to get constipated and she recommended lots of fibre, which only made me more windy and uncomfortable.
I have been eating low carb on and off for nearly 2 years and find my symptoms improve a lot, they basically disappear. Trouble is, I've cut lots of things out of my diet and now don't know what was causing the problem. I've cut out milk (but still have hard cheese and sometimes cream - cheese seems fine in small amounts, cream may be causing problems ie wind), wheat and other grains, potatoes, rice .. I've discovered this week that just upping my intake of milk chocolate made me slightly constipated 
Dark choc doesn't seem to cause the problem (90%).
A year or so ago I also developed a sort of strong cramp in my lower stomach, very low down (leaves me bent double and crying in pain) when I need a poo. Once I've been the pain goes.
Not sure if it's linked, but thanks to MN I've discovered I probably have some sort of prolapse (bowel) and not sure if that is linked.
Sometimes I also get an ache in my anus, which at the start is barely there, increases in intensity, then fades and goes. It's incredibly painful at its most intensive.
All this is making me really miserable. I've discussed all bar possible prolapse with my gp, but she says all is fine, it's just IBS. I have another appointment next week though, to ask about the possible prolapse.
Does anyone have similar symptoms? How do you handle them?
These problems are making me really miserable 
Anyone who's managed to treat their IBS by changing their diet, how did you find out what the culprits are? How gradually did you introduce foods?