Have you ever seen a specialist for these problems, such as a Gastroenterologist? If not, I'd recommend that you do so. They can prescribe medicine that can help those issues, but first they will want to have an upper GI done, at minimum, and most likely a colonoscopy as well to see if there are any signs of Crohns' Disease. IBS is diagnosed based on symptomatology alone, since there is no definitive test to do so.
In the interim, change your diet around and experiment with what is okay and what is not, as far as bland, spicy, oily, etc. You may have to eat the same or similar items consecutively to help determine what foods you react to in a bad way. Occasionally the Pancreas is responsible, and the GI MD will want to order blood work to help determine that as well.
Have you been checked for a hiatal hernia? Your symptoms sound very similar to folks that have one. Ask for an Upper GI, this is about the only to see if one does exist. if you do, it is not hard to handle with diet and exercise. I have one and it can make me miserable, but, I am able to keep it under control.