Each and every single time I get a sinus infection (at least 6mo a year i have sinus infections... hazard of living in a place with more mold than the 3 largest rainforests in the world, combined) it's exactly what you're describing. Right on down to the loose teeth. If you're feeling brave, tap yourself on the forehead or cheek on the side that hurts (warning... it will probably feel like lightening is shooting through your eyeball), and the side that doesn't (will feel like normal tapping).
See your doctor. There are decongestants that are safe to take while pregnant.
ANOTHER thing, though....
Prenatal Vitamins CAUSE headaches and even migraines in a LOT of women. if you're having steady or frequent headaches... stop your prenatals for a week. If the headache goes away... just chew children's vitamins thereafter. My highrisk office recommended Flintstones, but said any kids' chewable will work. You chew them throughout the day, so you don't have the WHOMP that hits your bloodstream.