If you don't have a cold, I'm guessing the sneezing and nose blowing are perhaps an allergy to something in your house. Since it wakes you up at night, I'd focus on your pillow, your blankets or possibly your laundry soap.
Animals sleeping on your bed could be another cause. An open window that would allow pollen to enter your bedroom may be the culprit.
Allergies can start at any time in our lives, so if you say you've never been allergic before, doesn't mean you can't be now.
In a prone position, our sinuses drain, often leaving us with a sore throat and phlegm that we cough up.
That you are feeling some regurgitation after eating and you've noticed that you are belching more could be an indication of a reflux problem.
I don't think the problems you've mentioned are related, but I would suggest you see a doctor.
I think your sickness is related to something wrong you have eaten.