Ever have a cough that doesn't go away?

Ive had a dry cough for over a year. Don't smoke or drink. Something is there, but never comes up. Ive been on Benadryl , robotussin, and now I drink a whole bottle of delsym The Delsym works best. A whole bottle is what it takes. Im serious. 

Gets expensive.  If I take too much Benadryl I go nuts and feel like im dying. Dextromethorphan does the trick but sooo much cost, Been to all the docs. Allergy, ear nose throat, going to a pulmonologist next week

They gave me tramadol, quasi opiate, took 200 mg to make the cough stop. So they can't help me. Already had surgery for a hernia. I take Pepcid. They say that can cause cough but Im 6 months out from the operation. 

It just started one day last year and hasn't let up at all.  Non stop all day, all night

Im going slightly insane from it 

Only when i have covid... 

I know people who have had this. It's just a bad habit. Constantly coughing or thinking you have to cough is self-perpetuating.

i don't know much about this stuff, but could it be a thyroid issue?