Fighting stress is not trivial. For those that stress is part of their mental disorder (i.e. anxiety disorders) is harder.
Diaphragmatic breathing is probably the most important factor towards less (greatly reduced) stress.
If you are physically unable to breath well, then you are fighting an uneven battle against stress.
If you think your nose is bloated, if you tend to breath from your mouth, if you can't smell well, you may have a crooked nose and/or chronic sinusitis (even worse!).
Siniusitis also results from allergies from what I've reading.
You may want to try Claritin (for allergic rhinitis), a safe antihystamine.
Anyways, sinusitis is an overkill, not being able to breath properly causes a great deal of stress.
See an ENT doctor to see if that's the case and discuss treatment.
Viable treatments include surgery or medicine. Decogestants, like Sudafed, mucolytics, like mucosolvan and expectorants, like guaifenesin are doing marvels with me, buy them in tablets, they are even sold over the counter, without prescription.
The most powerful of them is probably the decogestant solution, (i.e. Sudafed) but you may also get the rest too for a more complete approach. Nasal decongestants tend to be easily addictive, avoid them.
N-acytil-cysteine is a powerful mucolytic that is sold as food supplement, but in high doses can be oxidant and in any case it requires that you take at least three times more Vitamin C quantity than the n-acytil-cysteine to prevent n-acytil-cysteine side effects, but high doses of vitamin c can cause kidney stones (so better don't take n-acytil-cysteine at all).
Medicine is an excellent option and your doctor may not mention it, my ENT didn't mentioned it to me (because he has a monetary motive to do you surgery or because medicine is not appropriate for all, e.g. if you have problems with your heart). I had septoplasty but didn't help me much unfortunately. The pills though did marvels.
Medicine is also somewhat more inconvinient as you have to take pills once or twice a day for you nose to breath properly. BUT the difference with an unblocked nose is HUGE!