no it is not your batting, these machines have a long line of tension problems, I have had one for 6 years now and you just have to rethread everything and clean out the bobbin area often, change thread size that also has an effect on tension, be sure to use the same weight of thread upper and lower... you just have to walk away from it sometimes for your sanity..LOL... check your stitch regulater also.. I usually run mine just to the left of the top centerjust before the screw on the left top side.. my speed just before the last three dashes and I do not use a heavy batting, it does well on cotton or poly batting. email me if I can be of help.. Good luck..