I often wake up feeling like there's something stuck in the back of my throat, kind of like phlegm, but it feels more like a rubbery slime or clay. It's really making me feel nauseous and I'm wondering if there's any medicine to help with it. I've had sinusitis before, which got better, but this still happens. When I eat, I sometimes can't swallow properly, and other times my throat gets super dry, and I think some cough might have gotten frozen in there due to fungus or something. What could this be, and is there a treatment for it?