Brief Answer:
Please see the answer.

Detailed Answer:
Hi,thank you for posting your query on health care magic.

Looking at your symptoms,there might be following possibilities:
1.)Gravity
Your nose produces a rather astounding 1 to 2 quarts of mucus each day. Nasal mucus keeps the area moist and traps bacteria and small particles in the air. During the day, nasal mucus flows down the back of your throat and is swallowed. When you lie flat, mucus doesn't slide as easily to the back of your throat. You also swallow less frequently at night, so mucus can build up in your throat and at the back of your nose, causing nasal congestion and cough.

Blood flow to your nose also increases when you lie down because the flow is not impeded by gravity. This augmented flow can also increase nasal congestion .

Elevating the head end of your bed might help you.

2.)Low Humidity
Mucus needs to stay moist to flow easily to the back of your throat. Breathing low-humidity air dries nasal mucus, causing it to thicken or solidify. Humidifying the air you breathe at night and not overheating your bedroom helps prevent nasal drying while you're sleeping.Also you may use Saline Nasal spray while sleeping.It will help to maintain moisture inside the nose.

3.)Gastro-esophageal reflux.
The reflux of acid may lead to congestion in the nose and irritate the airway leading to cough.
Avoid eating spicy,oily,citrus food,too much coffee and tea,and caffeine containing beverages.Drink lots of fluids.Don't take heavy dinner .Take a minimum gap of 2-3 hours between eating and sleeping.
You may take Acid controlling medication like Pantoprazole.

4.)Post-nasal Drip-due to cold-it might irritate the airways leading to cough.In such a case ,you might be suffering from other symptoms like Discharge from nose,Nasal blockage ,etc.
If you are suffering from such symptoms,then you may take Oral decongestant(like Phenylephrine) if you are not hypertensive,Nasal decongestant drop like containing Xylometazoline and Oral Antihistamininc like Cetrizine.Also do steam inhalation,Avoid cold food and dust.Drink lots of warm fluids as they help in breakage of mucus secretions collected due to cold.

If you suffer from symptoms like high grade fever,wheezing sound in your airway,Severe breathing problem,Chest pain,etc then it would be advisable to consult a physician doctor.He/she might do Chest ausculation and a chest X ray to find out the cause.

Hope this answers your question.I would be happy to answer if you have any follow-up questions.Take care.

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