Sinus infections take a LOOONNGGGGG time to go away on their own. And if you don't get an antibioic, it may reoccur quickly (sicne you never got rid of the infection).
Sinus congestion - for me meant that my actual nose was not stuffed up, but I felt like I had cotton crammed in my head. My nose felt "full" and there was a ton of pressure. Got headaches, felt "fuzzy", NO sense of smell or taste AT ALL.
Sinuses are located by your eyebrows, on the sides of your nose, and I think there are some around your jaw.
That nasty green mucus when you blow your nose is a good sign of infection too.
Sounds like you might just have a virus. Water, tylenol, vit c and REST.