Ingesting air when eating is one of the contributers to the problem of reflux in infants. The stomach is very similar to a balloon. When it is filled with liquid and air, and pressure is applied (by lying on the tummy, a diaper that's too snug, positioning in sitting or with knees bent, or held closely against someone) the liquid can backflow or reflux. The flow may stop before it comes up to or out of the mouth or it may spew out of the mouth as vomiting.
Babies often swallow air when drinking. The Dr. Brown Bottle at http://www.handi-craft.com/ is the only bottle that takes air out of the swallow and is very beneficial for reducing reflux in many babies. I usually do not mention brands, but this is necessary to help answer this question.
I am a speech language pathologist that works with feeding disorders. It is important for parents to be armed with information about products that can affect the health of their child. I have NO connections with the Dr. Brown Bottle. This bottle is patented and is the only bottle with a laser cut nipple. Research reported on their site also indicates the bottle can increase nutrition.
Sensitivities/allergies/intolerance, preterm birth, and autoimmune disorders are other culprits associated with reflux. The duration of reflux will vary from child to child and will often depend on the causal factors and how they are addressed. Reflux can and often does disappear by 12 months of age. It is common however for adults to have adult onset reflux from gaining excessive weight and incompatible diets as they age.
At http://www.jacn.org/content/17/4/308.full.pdf+html is an excellence research-based review of reflux and its treatment.
Reflux can have very serious consequences, including pain, aspiration of acid/food/liquid into the lungs leading to infections/bronchitis/pneumonia; erosion of the tissue of the throat/nose/mouth (esophagitis), erosion of teeth, ear infections, and food avoidance.
Understand that medication my not stop backflow, but it does stop or neutralize the acid (depending on the medication). The acid is the source of pain, esophagitis, erosion of teeth and food avoidance. Basically, it reduces the refluxing to "spit" and we often say, "spit happens".
I suggest that you try the Dr. Brown bottle that reduces air intake when swallowing as well as continue the medication and strategies you are already implementing. Hopefully this problem will resolve quickly.