This is a condition called LPR. It is where a small amount of reflux is getting through the EUS valve (before the throat. The larynx then produces a clear mucus that is a natural defence against the acid to capture it. This mucus is copious and when mixed with the acid/pepsin/bile it has a bitter chemical taste. Do you get a slight pain below your left rib ever?
Treatment is trickier than traditional reflux. PPI's twice a day for at least 6 months. Regular bland non acidic fluids to flush out the reflux the right way and thin the mucus. Low fat, natural (clean foods) which are not too acidic. Chewing a little gum after a meal seems to help too.
If I have a bad day and the mucus has a chemical taste I often feel a little nauseous too. There is no real cure for this condition at the moment but with the right diet and approach it can be made less troublesome.
Stress also seems to make it worse so do your best to manage this.