How to stay eating healthy for IBS?

Hi All, I’ve had the worst flare, it’s lasted months and I can’t seem to fix it.
I struggle with foods, I don’t know what I“m allergic too and it’s my understanding there is no true allergy test you can do. The Dr has told me the skin prick test isn’t a true allergy test and doesn’t necessarily mean you’re allergic to it if you’re sensitive to it on your skin. My issue is is that I am terrible with food. I eat healthy but then I get super bored and want to try new things but what I’ve found is that the only things I can eat without upsetting my stomach are fish and sweet potato and I can’t live on that. Salad is fine sometimes, but I also want to put on weight and maintain it as I lose weight super fast, I’m 5’6 and weigh 53kg which is 116pounds, I’d like to just be a bit heavier but if I eat heavier foods, boom – I’m in agony for a month. I can eat bread but not pasta, I can’t follow the food map as it’s not right for me and I’m really lost! To top it all off my daughter has a terrible gut as well and she’s only 6 so I’m struggling for the both of us – any advice out there from someone whose been here with foods? What do I do? I’ve seen a nutristionalist and to be honest the 3 I’ve seen I learnt nothing from and they didn’t seem that knowledgeable especially with IBS… so going to the public, the flutherists… any thoughts, I’ve given up coffee, garlic, onion, most gluten, tea (boo) cheese, I“m pretty much on a miserable diet of smoothies, soups ( though they give me a sore tummy) and paleo food but I“m bored out of my wits and I still have a bad tummy. Getting a gastroscopy on the 28th May, I literally had to sleep sitting up last night as my stomach was so bad after I ate a healthy meal of beef scooped into lettuce with carrots and cabbage and some lemon juice! agh!