I second what everyone has said, get a referral for tests, dont let the GP fob you off.
Ive had IBS for many years, and I have to take penicillin twice a day as I have no spleen , which doesnt help.
I take acidphillus in tablet form once a day, try and eat little and often rather than big meals. Very little bread and pasta as it fills me up to quickly. I also try and eat a very healthy low fat high veg/salad/fruit type of diet, but this is a double edged sword as I have to be very careful how much fresh food I eat. I also avoid beans/lentils etc like the plague. Stress is also a huge trigger.
I was lucky to be referred to Dr Peter Whorwell who is a pioneer in hypnotherapy for IBS, he immediately told me to stop eating "healthy" food and to eat more processed food as my body was less able to digest unprocessed food. This does work but I dont like to eat very much processed food.
The hypnotherapy I was taught helps me manage my pain, I also take spasmonal when I feel an attack coming on and I drink lots of peppermint and ginger tea. Exercixe also helps, I run.
Once you are absolutely sure its IBS you will be able to slowly try and find a diet that works for you.
I still drink wine :)
good luck