I have a fish smelling discharge and went to several doctors and all of my paps came back normal with no std?

I've been having a not so pleasant discharge (fish smell) to be exact. I been to several doctors and got tested for every STD and all of my pap's came back normal with no STD. I had a l ultra sign done and I had free fluid around my left ovary. My doctor thinks that a cyst has burst but that don't explain the fish smell! I have to take at least 2-3 showers a day just to feel clean or to make sure the smell isn't so loud. I'am so fed up with the discharge and the smell i can't take it anymore! He now wants to do a dnc where they scrap all of your tissue in the cervix because he thinks that the bacteria is in there and causing the discharge! Do anyone have or had this problem? can you please tell me whats going on???!!!