I had that problem. I tried baking soda, vinegar, all that. I had to pull out the cover that fits inside the drain to the garbage disposal and clean it off (I think you said you did that already), then I looked down in there with a flashlight to see if there was junk in there than needed to be removed. Then I put about 4 lemons down there, 1/4 at a time, and ground them up good. I ran plenty of water through there while I was doing that. I also ran some ice cubes through and that helped a lot. Take off the drain cover thing and put a handful of ice cubes down there, replace the cover, and carefully grind them up while the cold water's running. Just be careful not to put too many down at once, or else your motor will have to work too hard and you could blow a fuse or something. The ice chunks plus the lemon can usually clean it out pretty good. If that doesn't do it - you may really have something blocking it up that you'll need to get removed. Good luck!