I don't have a sinus infection, but i have smelly, green mucus. what could it be?

And your proof: That it is not an infection? Allergy, autoimmunity may cause inflammation, but green slime sounds like infection, either bacteria or fungi. Get a culture and post the proof. See an ENT doc for management, possibly including surgical exploration and drainage.

Need to see MD: Smelly green mucous may represent chronic sinus problems and you need to a physician to diagnose the condition and then treat it with appropriate mediications.