I have to guide the fabric through the machine otherwise the needle just goes up and down in the same spot. Maybe I'm really pushing it too fast?
If this is the case, then the fabric is definitely being stretched when the dog feet are trying to pull the fabric through. You need to do what you can to eliminate the weight of the quilt from dragging the fabric from the sewing area. Put a table or TV tray behind your sewing machine and another to the left of it to rest your quilt on while sewing on it. That might help too cause even if you get a walking foot, if the weight of the quilt is pulling that much, you are still going to have problems.