oh Luv.. coughs are the worst.. I'm sure you've tried all the usual things, I had a bad cough a couple of years ago for 6 weeks, I had to have steroids to get rid.. A damp towel on the radiator can help put some moisture in the room and lessen irritation on airways... Also sleep propped up, I used to use a floor cushion and then a pillow on top...them sudafed plug ins work wonders for MiniNova, but not sure about adults!!
Hope you get better soon x