I'm trying to figure out the root cause of this really bad cough I have
- this is the second time I've had it now.

It's a deep, choking, gagging cough, very like the kind of cough you'd
get if you were genuinely sicking up - but no nausea and no stomach pain
- and sometimes I do vomit.  I find I'll stretch my head up, or lean
over, when coughing.  Often a fit will end with a gag.  It is usually
preceded by sometimes a very sudden, severe back-of-throat tickle.

I've had chest x-rays and they were clear.  I have acid reflux but I'm
not sure that's causing it.  I was treated for a bacterial infection the
last time I had this, during the antibiotics a really nasty, thick gross
mass was ejected from each nostril over two days.  Dr. said that was
normal (?!) As I hadn't connected sinus problems to the cough, I can't
remember if the cough got better at that point, but my chronic very
low-level sinus issues (bit of a blocked nostril in the morning which
clears up with the shower) went away during the antibiotics (two months
worth!) but came back after.

I do currently have a post-nasal drip and stuffy nose, but no severe
sinus symptoms.  It never really occurred to me that this might be sinus
related, as I've never heard of a cough this bad being connected to
sinus problems.

Until now, when I've been doing some internet research.

Could such a horrible cough really be caused by something as common as a
post-nasal drip?  What can I do about it?

jmc