Hey, i can understand what you're feeling. I too get scared when i have a phlegm related cough or bronchitis which makes it drain constantly into my stomach.
I don't know if you or anyone else on here has heard of activated charcoal capsules. I take them fairly regularly. All they consist of is a plain gel capsule, filled with activated charcoal powder. I was introduced to them by a co-worker many years ago when i had very bad N*, so i took 2 of them, and (no lie) in less than a half hour it was gone!!
After researching them and using them for many years, i've come to find that they help with almost any digestive disorders, from severe N*, to indigestion, diahrrea, hearburn, etc.
I used to practicall live on pepto bismol (ICK!!), but since i've found the char-caps, i use nothing but that, for everything stomach related.
My reason for telling you this? Well, charcoal adheres to the fluids and foods, and excess acids in the stomach, and safely passes it through the intestines. So when i have extra acid (reflux), diahrrea, or excess phlegm in my belly (like you're describing above), i take the char-caps, and my stomach feels so much better and it seems to pass the phlegm into the intestines and it's on it's way out! hehe!
ONE PERCAUTION!!! DO NOT take char-caps at the same time as any other type of medication, because it will bind to the medication and not let it absorb into the bloodstream as it should, it'll just pass it right out of your body. You should take the char-caps 2 hours before or after taking any other medication.
It is safe and natural, and it works great for gas too! lol!
For God has not given us a spirit of fear; but of power and of love and of a sound mind. 2 Timothy 1:7