I had something similar. My ENT told me that the two main causes of persistent throat-clearing are post-nasal drip and acid reflux. Sometimes the post-nasal drip can itself be an effect of acid reflux, as the nose generates extra mucus to neutralize the acid.
The body typically generates about four pints of nasal mucus each day, most of which is moved to the back of the throat by microscopic hairs and unconsciously swallowed. If you develop a swallowing disorder, or if the mucus becomes thicker or heavier for some reason, then some of the mucus can end up in your throat or bronchial passages. From your description, it might well be post-nasal drip which is the source of the whole problem.
You can rule out acid reflux (most likely LPR, if you have no symptoms of heartburn) by taking a PPI to suppress stomach-acid, and seeing if that makes any difference. But a simpler (and safer) approach is to try an anti-histamine to suppress the post-nasal drip and establish whether that is the source of your problems. One of the best for post-nasal drip is an azelastine-based anti-histamine (marketed under the name Astelin or Azep etc) in the form of an intranasal spray. If your post-nasal drip is due to allergic or vasomotor rhinitis, then it should be eliminated or greatly reduced.
Your investigation should not stop there, even if the anti-histamine relieves symptoms. You should find out what, if anything, you are allergic to, and if so why your histamine-tolerance decreased a year ago.
In my case, Astelin did relieve symptoms but I took it only for a week because it made me drowsy (though it is not supposed to). I was allergic to dust-mites, but the ultimate cause of my lower histamine-tolerance was B12 deficiency. The further back you can trace the source of your own symptoms, the easier it is to treat.
