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Yes, it sounds like you have a sinus infection as it classically causes headaches (sometimes face pain or pain in the upper teeth), mucous discharge, sneezing, sore throat and stomach upset from the swallowed mucous. This can go on for months if not treated. I would suggest you see your GP and get on antibiotics and a decongestant. Treatment can take 2-3 weeks.
You're welcome. Hope you get the care you need and are feeling better soon.