Is the problem with your feed dogs or with the feed mechanism of the walking foot. Do you have the same problem if you use a regular sewing foot (I mean right now, if you take off the walking foot and replace it with a regular foot, is your stitch length correct or is it also very small?)
Check the pressure on the presser foot, if you have that adjustment, to make sure it is high enough. Also make sure your feed dogs are engaged. Sometimes, If you have been doing free motion quilting, it's easy to forget to re-adjust those settings afterward.