I am not familiar with oregano oil being particularly strong against bacteria. It is much stronger and most often used as an antifungal. Because it is very hot going down, it can also cause discomfort in people who can't tolerate that, so be wary. I've used it for fungal infections, but again, there are stronger antibacterials out there.
Most people think that the main culprit of heartburn is food, and that could be. Certain foods can relax the LES, either by relaxing the surrounding muscles (which is what coffee, alcohol, chocolate, and peppermints do), or by irritating the esophageal lining ( some problems are tomatoes, citrus, onions, and peppers). There are other triggers including being obese, or even just a few pounds overweight.
The bigger your belly is, the more pressure it puts on the LES, allowing stomach acid to splash back up into your esophagus.
Do you have a hiatal hernia? That can cause acid reflux.
The following can cause acid, Nitrites usually taken for heart disease,
calcium channel blockers, for heart disease and high blood pressure,
birth control pills, benzo-diazepines Valium and Ativan for example, and
tricyclic antidepressants like Elavil.
In a dehydrated state, the stomach will be unable to make the mucous lining that protects the stomach. Water intake will help nearly any condition, including GERD, ulcers, and other gastrointestinal problems. How much water should you drink? Take your weight in pounds,
divide that by two, and that number equals the amount of water in ounces you should drink daily. (If you have Kidney problems talk to your Dr.)
Do you have any food allergies?
Try marshmallow root, (real marshmallow root, from the actual marshmallow plant). Marshmallow root is part of an herbal group called demulcents soothing substances that quiet inflammation in mucous membranes, including those in your digestive tract and esophagus. Demulcents actually coat, soothe, protect, and repair your mucosal
membranes, which heartburn can irritate and damage.
Try taking 3 to 5 g two to three times a day. Other good
demulcents include aloe vera gel and deglycyrrhizinated licorice.
Have you had your B12 level checked?
Many articles have been written about gastrointestinal bacterial overgrowth
due to the use of antacid drugs. Bacterial overgrowth is common in irritable bowel syndrome, Crohn’s disease, and ulcerative colitis.
Have they checked your stomach PH?
Some info. on H.pylori bacteria. ADP, which is oregano oil from Biotics Research, two capsules twice per day along with an herb called mastic. MegabMastica, two pills twice per day.
You would need to avoid sugars, salt, flour and oils during the two-week treatment period. (For H.pylori treatment.)
Forgot to mention one other common remedy -- slippery elm bark.
Good decision to stay away from the buttermilk -- dairy further inflames the digestive system, and most people have a hard time with it even when they don't notice it. Don't really know why any of the three things you're avoiding would have anything to do with an ulcer, and would wonder just how thorough your testing for h pylori was -- after all, there's a reason it took so many years to figure out it was a major cause. The old fashioned allopathic way of dealing with it is to take antacids, such as Mylanta. The newer medicines are protease inhibitors and other acid suppressants. While this can be necessary if you have bleeding so you don't bleed to death, in the long run they force the stomach to produce more and more acid so you can digest your minerals and protein, as it has to overcome the suppression to do this. The natural way to deal with it is to learn to relax -- meditation, exercise, and the like -- as stress is a major way to cause a breakout (we all have h pylori running through our systems -- the health of our stomach and intestinal lining and of our probiotic colonies determines if it finds a nice home inside of us), and there are several natural remedies you can combine or try separately to see if they help. The main ones are aloe vera juice inner filet and DGL, a form of licorice. But there are others, although one of the reasons some work is because they are toxic to h pylori, including mastic gum and manukka honey. Cayenne is also a treatment, but if you can't handle the heat it might make you feel worse. I'd say that if allopathic medicine isn't helping, and they haven't recommended surgery, then you might go see a naturopath or practitioner of integrated medicine and see if you can't find a diet and some natural medicine that will work better. Good luck.