Hi,
Fodmap doesn't work for everyone, including me. Consult a Gastrologist and or Dietitian for help. There are treatments ranging from fecal transfere to dietry changes. I use laxatives and any food source that I have found helps, such things as green pears, green netarines, prunes, peanuts, tinned peaches with bran flakes and liquorice etc. There are pros and cons to such foods like too much liquorice is not good for us, red is better than black, prunes are high in sugar and calorie content, not great for diabetics like me. I don't do it all with laxatives for fear the muscles will get lazy and require more laxatives. Obviously stay away from foods that bind you up and keep drinking plenty of fluids. Try to eat more fiber, not something I have been able to do. I eat a lot less and try to consentrate on high protien foods like eggs and sardines with a little red meat once a week, you should be fine with chicken. I have problems with a lot of veggies and only eat carrots, onions which are mainly cooked but raw occasionaly as they are a prebiotic and a digestive, peas are on the list I shouldn't be eating, but I'm fine with them and bread, I do use wholemeal with seeds as my main food item.
Alot of medications have constipation as a side effect. I use omeprazole, domperidone and acidex to try and be comfortable. I have found I can tolerate foods that are not supposed to work with IBS and foods that are supposed to be good don't work for me, so it is vey much an individual thing. Have your B12 levels checked as with stomach problems this can be low and can lead to more serious health complications. To soothe fissures around the rectum I use Johnson and Johnson's aloevera hand moisturiser, it gives instant relief and is not messy like vasaline.
Life very much becomes a balancing act to keep myself between C and D, too much or too little and I can go either way. I increase fluids and fibre in the summer to offset the increased fluid loss from the heat. In the winter I mainly consume home made veggie soup finding I can tolerate more veggies that way and it is not high in sodium as canned soups are. I have found garlic and ginger helps to settle the stomach a little but when it fails to do the job it is into the hard core treatments. I will not go more than 2 days without taking serious action to empty the bowels as after 2 days it starts getting critical for me. I can be constipated and still have D, this is called flow past which can leave me blocked but still expelling something. Definitely not a place to be. When this happens it is supository time.
The worst thing you can do is nothing, the sooner you work around, manage IBS the better you will cope. I have been through it all and now have a totally corrupted digestive system from IBS and Autonomic Neuropathy. No cure and no treatment, just left to manage as best I can. My rule of thumb, if it makes me comfortable, eat it, otherwise don't eat it again.
Cheers