I know this is a little bit of an old question, but since none of the existing questions are accepted, I'm going to make a run at it.
In a comment on virolino's answer, the OP says
Problem is that there is nothing really to "blow".
As someone who has had sinus problems my whole life, this has 3 possibilities I can see. I'm not a doctor, so there's probably other options, too.
- With changing position, the contents of your sinuses are moving around. Try blowing when you are laying down, if you haven't already.
Does rolling onto your side(s) or stomach change your ability to breathe?
- You might have something in your throat, like an extra flap, that's closing when you lay down, hindering your breathing. There's already flaps in your throat to do this sort of thing. If you don't use them properly, or if they are somehow damaged and don't respond appropriately, they could be causing problems. You should see a doctor about this.
Is it only in your bedroom or anywhere you lay down?
- If it's only in your bedroom, you might have some allergies. It could be your bed sheets, as others mentioned, or it could be your mattress, pillow, carpet, or 1000 other things. If you have a lampshade nearby, it could be dusty and causing this reaction. I used to read paper books, but the dust/mites and the mold (warm & humid climate) would drift off as I read, falling on the pillowcase and sheets, so even when I wasn't reading, it was still an issue. I tried wearing a dust mask to read, but that didn't help the dust on the sheets. I've also been allergic to the pillow itself.
If it's anywhere you lay down, see option #2 above.
To address the dust/mites/mold issue, I stopped reading paper books and went strictly e-books. I still like having books, but I have to keep them in a fully enclosed/sealed bookcase so they don't cause me problems.
I also wear BreatheRight (sold at most department type stores such as Walmart, Target, and CVS) strips to bed. They open my nasal passages to allow more airflow. When I first tried them, I found that I was more fully rested while actually needing fewer hours of sleep. I'm not saying this will fix your issue, but it's about the only "LifeHack" thing I can think of to try, and it's still not a real lifehack.
This seems more like a medical condition you need to see a doctor about. Consider talking to them about seeing an allergist to determine if that's even part of your issue.
I hope you've tried the medical route in the past month, but if you haven't you should. If nothing else, it'll help you rule out possibilities.