If you have loops on the back, then your top tension is off. It is too loose. Just to make sure, i would thread the machine again and make sure that is correct. If the problem continues raise the top tension by one number or notch. Sew and see if that helps if it does lessen the loops on the back keep adjusting till it looks good.
Try and use a sandwich of backing batting and material to sew on while you do your tension adjustments.
Sheila