This could be due to side effects. If you started any new medications etc. as this could be due to that. Also this could be related to your sinus cavity/mucous membranes as well, which could be caused by an infection as this can cause a change in your sensory that allows people to smell as it's not functioning properly.
At this point, do follow up with an ENT (ear, nose, throat) doctor for further evaluation.
Best of luck Hun, Hope this helps, If you need anything else please feel free to ask. If you found this helpful don't forget to click the *ACCEPT* button and leave *POSITIVE* feedback.