I think you need to see a new doctor.
Unless you have some other symptom(s) you haven't listed on here, I think he's full of it when he says that your symptoms can't possibly point to a bacterial overgrowth. There are several people on here who have had bowel problems (can be either C or D) and pain and gas and bloating--in short, your symptoms--and they have taken the test and come back positive for bacterial overgrowth. There's also the chance you may have h. pylori--the leading cause of stomach ulcers. I know stomach ulcers hurt higher up and there are some people on here who have been diagnosed with h. pylori who had a lot of pain, nausea, indigestion, etc.
I think he's also wrong about the fiber. Now, I'll be the first to admit that fiber doesn't help everybody. Fiber supplements managed to make both my constipation and my diarrhea worse--it may indeed be making you worse too. But, again, there are people on here who have gotten some relief from taking fiber--not just from bloating, but from pain as well, in addition to better bowel movements. There are a lot of different types of fiber out there too, so if you haven't seen any benefit from your current brand, you may want to try something else. Pysillum husks seem to be the local favorite. But yes, they can help relieve pain, depending, of course, on what's causing your pain.
Unless you have problems with constipation, try the Caltrate 600 w/ vitamin D; it helped my bowel pain.
If you have a wheat allergy like Celiac's disease (my cousin's husband had his GB out because he had all the symptoms of a bad one, only his symptoms didn't go away afterwards and they finally diagnosed him with Celiac's and he's much better now without gluten), just reducing wheat probably won't help you much, if any. If he suspects you may have a wheat/gluten allergy, you should try going off all gluten for a couple of weeks and see if you improve. Some people find they just can't digest wheat/gluten even if they never test positive for any allergy. Other things you can try eliminating (but not all at once, or you won't know what the real culprit is) are artificial sweetners, dairy (some people are only intolerant to the lactose, but some are intolerant to the milk proteins, including casein, a common ingredient in a lot of pre-packaged foods), real sugars (honey, cane sugar, fruits and fruit sugars in general) and meat, starting with red. If none of that helps, and you can afford it, try going totally organic. Some people are hypersensitive to pesticide residue, growth hormones and antibiotics in meats and/or preservatives and dyes. My mother's doctor recommended organic for her after she was diagnosed with fibromyalgia because they have found that the chemicals in food can spark a pain episode in fibro patients.
You doctor sounds very unsympathetic and dissmissive. I bet he wouldn't tell someone who is presenting with chest pains just to up his dose of aspirin to get rid of the pain. You are hurting for a reason; your body is trying to tell you that something is wrong. He needs to be exhaustive in his attempts to figure out what's wrong. Only after he's tested for everything he can think of and it's all come back perfectly normal should he give you medicine to try and override the pain. Sometimes our bodies do go haywire and hurt without cause, and sometimes we have something wrong with us that modern medical tests can't detect, but more often than not there is a cause and we are able to find it. Unfortunately a lot of bowel problems are hard to treat, but knowing what's wrong and at least making some progress towards making it better helps.
Doctors generally don't like the internet because patients who are chronic worriers will look up their symptoms and find they match some rare, deadly disease and get themselves worked up into a tizzy when the real disease is something common and simple. But that doesn't mean the information out there is false. It's best not to try and diagnose yourself, but I don't see a problem with looking for a treatment for a known problem if my doctor can't supply one. My first rule of thumb for reading medical information is "does it make sense?" If it doesn't make sense, then it's probably bunk. Another indicator of bunk is a disease or symptoms that can only be cured by this vitamin/medicine/herb/tea that only we sell. But there are a lot reputable websites out there--the most prestigous of which are by known medical institutions (like the Mayo Clinic) or known medical publications (like JAMA).
Talking to people on this forum and trying their recommendation of calcium is what got me over my bad pain and diarrhea spell last summer. I don't think positive results are rubbish! If you can, you may want to try a different type of doctor all together. I'm thinking the term is homeopathic; Sarita would know because she's looking into becoming one. But basically they try to treat the whole person, not just the symptoms. So rather than dosing you up with meds, they try to figure out what's causing your problems in the first place and eliminate that. And they may help you make lifestyle changes to help your problem or to keep it from coming back. They're real medical doctors, so hopefully your insurance covers one. There's also the holistic route of acupuncture, meditation, yoga, tai chi, organic foods, etc. I won't say that they are the options of last resort, but I do think it's important that you are properly looked at first. Acupuncture won't do a thing if you have an enlarged liver.