Are you having difficulty breathing even if breathing through the mouth? Or only if breathing through the nose?
Thank you for the additional information.
There are several different possible causes of these symptoms. Yes, it could be an infection of the nose or a sinus infection; indeed, it could be both, as many sinus infection occur in the setting of an infection of the nose. An allergy can also cause significant inflammation of the nose, and would commonly cause congestion, sneezing, and mucus, but does not cause painful bumps as often as does an infection. It is a good sign that there is not any shortness of breath when breathing through the mouth. Congestion of the nose and head can affect breathing through the nose, but if the shortness of breath is present when breathing through the mouth, it would suggest that there is extension into the lungs. Ultimately, it would require an appropriate evaluation to determine the exact cause, but it would be reasonable to try an antihistamine/decongestant to see if the symptoms can be controlled.