A syndrome is a collection of symptoms that can't be attributed to a specific condition, so there's no specific test for IBS and, in the absence of anything else particular, if you go back to your doctor that could be the diagnosis.
A lot of people suggest a FODMAP diet for IBS, which is eating foods low in a particular type of carbohydrate. It really needs specialist advice to make sure you are eating healthily and not removing too many items from your diet. I looked at this, but I was ok eating the foods on the 'try to avoid' list and can't eat some on the 'good' list.
My GP suggested trying a food combining diet for my IBS, and it made a massive difference from being doubled up with pain and regularly dashing to the loo. He said to get the book The Harcombe Diet, ignore all the guff in the first half and go straight for the eating plan. You need to read up for the details, but basically, it's low salt, low sugar, avoid processed food and eat food groups together that are easy to digest, eg carbs and veg, protein and veg, and fruit before or between meals. After ten days I felt much better, and still stick to it closely now; I still have bad days, but overall my symptoms have never been as consistently bad as the early months.
Keep a food diary for a while and see what the triggers are. If you start cutting out too many foods you may not know if it's a certain food or the combination.