Ive been having a bad headache with pressure in top teeth. i went to dentist for my exam and cleaning few weeks ago and it was good, no issues. i was recommended sudafed and that has made my headache go away. could it be my sinuses?

Yes, I think it is possible. From what you have described, pressure on top teeth, this would make me believe that there is a problem with your sinuses. Please seek out consult with Physician, who could advise you on next step.

Cold be. Sit down, bend over, so that your head is between your knees. If pressure increases, it's sinuses. That said, if you have a sinus infection it requires treatment.