Do you have the same morning congestion?

Every morning, I wake up with my nose very congested, and with pus in my throat, and I also have to hack out the yellow snot aculated in order for me to breathe well again. I don't ever have to do this during the day, it's basically when I wake up. Somebody told me that a doctor suggested the pus was caused by night reflux; could this be? Is the congestion maybe caused by allergy? Any serious suggestions are welcome.