Although patient with band slippage can suffer from some of the symptoms that you are describing, most commonly they also have some degree of pain. Without knowing much about you it is hard to guess whether you have band slippage. Food intolerance and a rapid increase in reflux and pain often can be an early indication of slippage, but most patient with slippage will describe an event which prompted the symptoms, ie..., vigorous vomiting after not chewing their food well or eating a larger bolus of food that they could not easily get down.
My recommendation is to go see your doctor ASAP, or start seeing a new doctor that is not judgemental and wants to see you despite your occasional shortfalls and let him help you get back into the program and get the band back inorder. Gastric band requires a lot of effort for it to work well. It needs a motivated patient and a strong doctor-patient relationship for this to work.
The problem will be confirmed with GI series or endoscopy. Through the endoscopy procedure, the slipped band would be raplaced but Dr will decide to replace or perform another surgery.
Most band problems can be diagnosed with a simple upper GI series X-ray. In this test, you drink liquid barium and radiologist takes images as it passes down the esophagus, and through the band, into the stomach. If it turns out that your band has slipped, it can be re-done with another operation. Unfortunately the probability of re-slippage is fairly high.
You should get this test as soon as possible. Night-time aspiration can cause pneumonia and lung abscess. You don't want that.