I was diagnosed with IBS aged 17, it keeps me thin is my only consolation. I'm 54 now and not got any real help with it ever.
As you're at the start of your IBS journey, you probably are full of hope and faith in the health services. I'd advise you to curb your expectations, not because you don't need help, but I don't think the NHS will help you. IBS is a diagnosis given mostly to women because they don't know much, all clinical studies used to be exclusively on males until the 1980s or 90s, so how women's often delicate digestion is disrupted by hormones is understudied to say the least. Hence the IBS which stands for "I don't know" to my dyslexic eyes.
Tests showed erosions in my oesophagus and stomach lining but no ulcer the day they looked, which was four months after I collapsed for 3 days on holiday with the pain from a suspected ulcer. Colonoscopy was excruciatingly painful, they pump litres of air into you regardless of your own small size, but with normal results. I've two benign tumours on my liver and one on my adrenal gland, just observations as they search, I've probable intermittent paralysis of the middle section of my gut. That means no constipation or diarrhoea 95% of the time, just pain and more pain.
All I've ever got to help after the array of tests that show nothing wrong, is omeprazole. I don't take it because it makes me feel sick and I already feel sick a lot.
I consulted a private dietician who told me to stop following the GP's advice of eating so much fibre. She said my diet contained far too much fibre (I'd been told to increase it many times and had done so each time) and even someone with no underlying problems wouldn't handle that much fibre! She took me through a three month elimination diet which basically showed I react to food. Less food means less pain, more food means more pain. Eating wheat once is ok, eating wheat once a day all week will be bad and I'll have a lot of bloaty pain. Cheese and butter are ok in limited amounts, milk or cream are bad. Nuts sometimes give me allergic reactions, so I can't eat those. Foods like tomatoes, potatoes or oranges make me itch if the juice touches my skin but I eat them anyway. I've got to eat something. Some days all I have is some fruit. Fruit seems ok for me, broccoli rice and carrots are ok too, but I must keep changing what I eat or it will cause problems, with limited choice it's hard to do and I've the rest of my family to cook for as well.
Like I said, it keeps me thin, but the medics haven't been much help at all. I stopped going back for their tests ten years ago and got no better and no worse since. The tests were not designed to find women's problems so not surprisingly they don't.
