Embarassing Abdominal Noises and Gurgling

Since September 2009, I have been having terrible abdominal noises. I can feel my abdomen spasm when it makes loud gurgling and farting noises. However, I am not farting. Sometimes, it makes high pitched noises that are almost like a hum. I visited a general practictioner who prescribed me Hyomax which is supposed to slow down the intestinal spasms. However, it is now December 2009 and the abdominal spasms and gurgling have come back. I am taking probiotics and taking fiber tablets and nothing seems to work. These noises are so horrible that I dread going to work because I don't know when my intestines are going to make embarassing noises. I know that my co-workers are thinking that I am probably farting. Please tell me what I can do to reduce these intestinal noises? Are there medications, diet modifications, or exercises that can help?