Tickle in oesophagus causing cough for last 3 years

I have been getting the same tickling feeling in my oesophagus for the past 3 years which causes me to cough. It is worst in the morning and evening. Sometimes throat feels sore and have the need to swallow when nothing is there. I have been assured time and time again that it is either silent reflux of post nasal drip causing the irritation. However I am currently around 5 months in to my latest experience of this issue and omeprazole and mometasone is not having any effect. Has anyone had a similar issue? What tests could I request / medication could help?