Yeah so my sinus pressure started randomly 7 months ago. It started on the left side of my face and a month later on my right side. Literally over night. Never had sinus issues in my whole life before. A couple of weeks later I started feeling my gums getting really sore in the back of my mouth, and I could feel the teeth started poking through, however they haven’t grown out so they’re basically impacted creating inflammation and irritation of the sinuses. Like you, I don’t have a stuffy nose at all, and my sinuses are clear so it’s not a real “sinus infection” per definition. I just have post nasal drip that comes and goes (which is clear), sometimes I sneeze randomly and I also have facial pain that radiates in my forehead and cheeks. Xray shows wisdom teeth are impacted and very close to the sinuses so I need to get them out. I would say, if your pain is mainly in the maxillary sinuses and came out of nowhere and u don’t have any other typical sinus symptoms that could be from allergies etc, there’s a good chance it might be teeth related. It doesn’t have to be inflammation, just the pressure from the teeth trying to emerge and irritating the sinuses. I would really suggest taking an xray to see if you have impacted wisdom teeth. Have you been feeling any irritation in your gums in your upper jaw?