Well if you only get stuffy when you are laying down, I'd say maybe you are having some sinus issues or a minor allergy. Is it only in bed? Have you washed the sheets lately? If so did you use different soap or fabric softener? Did you line dry or put them in a dryer? Do you have pets? Are you getting good sleep or do you wake up tired? Are you able to sleep through the night? Do you wake up in the morning with a sore throat? The more details you can provide the better.

I never once had an allergy problem, last year at my HIGH stress job I got what I thought was a miserable summer cold I couldn't kick. I went to the doctor and was diagnosed with "Stress induced allergies." I took a Claritin a day for like 10 days, cut back some work hours and everything worked out...