For a quick and cheap way to freshen the air in a room, add a few drops of essential oil to a spray bottle of clean filtered water and spritz around your house (especially on curtains and upholstery).
A great way to add a pleasant scent to the room when vacuuming is to add a scented dryer...
I have faced a similar issue in the past and I took my pet to veterinary hospital and they treated her. It was due to some injury for which I was clueless.