First of all, I'm not positive whether i have a sinus infection or something wrong with my tooth. This is the third day i've had a problem. The first night i started having a pain in my upper tooth/teeth. I looked into it on the internet and it sounded like it might just be a sinus infection. I blew it off and went to sleep since i hadn't had much sleep due to my grandmother being in the hospital. The next day i had definite sinus pressure all over. I tried drinking hot liquids and taking a long hot shower to relieve the pressure. It seemed to work pretty well, started getting lots of drainage. The next morning (today). There is still very slight pressure (hardly any)and still some pain in the tooth. It's my upper rear tooth that has had a cavity filled a long time ago, so i would assume it isn't anything to do with the filling. Is there anything that would help diagnose what it is without going to the dentist?