A: Postnasal drip can be due to food sensitivities, or to allergies, things that you might be allergic to in your environment. It could be exposure to mold or yeast. I would look into those types of things.
H. pylori can cause issues with histamine. You might be producing excess histamine, and that might be causing you to have this excess postnasal drip as well. I would consider looking into treating H. pylori. I do have a comprehensive article on H. pylori that you could read through, which will give you a protocol that can be utilized for about two months, and that should produce a complete resolution of H. pylori. I'm curious to see if your symptoms will improve after that.
Again, this can happen because of food sensitivities. H. pylori is a big promoter of those, and histamine issues can come from a variety of things, including mold exposure and H. pylori infection.
I would definitely address H. pylori. I'm working on a program that's going to focus on H. pylori, as well as other gut issues. But I also have everything that I pretty much use for H. pylori in my article linked above.