Had the sleeve over 4 months ago and am having issues with eating, nausea, vomiting and have air caught in my esophagus. Advice?

If  dilations were performed it  means  that either narrowing (stenosis)  or a hiatal hernia was found, if you have not yet had a barium swallow (upper GI series)  under  fluoroscopy (X-Ray), you should get it This study will give  information  as to the nature of your obstruction, for example if you have a hiatal hernia   it can be fixed surgically  at any given moment (“the sooner the better”), any other anatomical problem is found, it  has to be evaluated carefully  before deciding the best treatment option.

It sounds like you are experiencing significant post-surgical complications that have not been fully resolved despite multiple interventions, including dilation and correction of a fold in your stomach. Given that your symptoms—nausea, vomiting primarily consisting of phlegm, and trapped air in the esophagus—persist despite slow eating, small bites, and gas-relief medications, there are several potential underlying causes that may not have been fully explored.
One possibility is a persistent functional or mechanical obstruction, even after dilation. Some patients continue to experience narrowing due to scar tissue formation or persistent folds in the stomach, which could require further intervention. Another potential cause is gastroparesis, a condition in which the stomach empties more slowly than normal, leading to nausea and vomiting. A gastric emptying study would be necessary to confirm or rule this out.
Another consideration is vagus nerve dysfunction, which can occur after sleeve gastrectomy and result in delayed gastric emptying and difficulty tolerating food. If this is suspected, motility studies may be beneficial. Gastroesophageal reflux disease (GERD) is also a common issue after sleeve surgery and can contribute to excessive mucus production, nausea, and the sensation of trapped air. If reflux has not been thoroughly evaluated, a pH impedance test or Bravo capsule study could help determine if acid or bile reflux is contributing to your symptoms.
Additionally, esophageal motility disorders, such as achalasia or hypercontractile esophagus, can cause difficulty swallowing and persistent regurgitation. You mentioned undergoing esophageal manometry, but if symptoms persist, a repeat study or a barium swallow may provide further insights. If a hiatal hernia was not checked during your previous evaluations, a barium swallow study would be helpful in assessing for this condition.
If bile reflux is a concern, which can sometimes occur after bariatric surgery, it may be beneficial to trial a bile acid sequestrant or sucralfate in addition to proton pump inhibitors (PPIs) to determine if this improves your symptoms. If you are not currently on a PPI, it would be reasonable to discuss initiating or adjusting one with your physician.
Since your current doctor has indicated that they are not planning further interventions unless symptoms worsen, seeking a second opinion from another bariatric surgeon or a gastroenterologist with expertise in motility disorders may be beneficial. If you have not yet undergone a gastric emptying study, pH impedance test, or repeat barium swallow, these tests would be important next steps in fully evaluating the cause of your symptoms.