Please help with my constant nasal drainage which only opiates help?

I have a constant nasal drainage in the back of my throat which I cannot cough up or blow my nose, it continues all day and fills my stomach up so badly that I throw up all that mucus or snot. The only thing that has helped is opiates from pain meds. I have no idea how or why it works but I need to have this fixed so I don't have to depend on the opiates. I have been to an ent and found nothing wrong, This has been going on for 8 yrs and I beg of anyone to please help me.