Discharge and Odor..Please Help?

Okay so this is going to obviously sound yucky but i really need advice. I get regular check ups wiith my OBGYN for STDs and paps and i have had the same partner since forever who gets checked with me. We are both clean and have nothing.But For the past month i have been getting this foul gross odor down there i can hop in the shower clean like crazy then hop out and it comes back.The discharge is clear and its what smells so bad. I have the Mirena BC so idk if it could be that thats causing this smell? I have no pain or during . But i dont even want to have because its embarring the smell is strong best way to discribe it is Fishy. SOO if its not a STD what the hell is it?! Its made me so insecure n i cnt even have :( What could be causing this?