It could also be the thread. What thread are you using top and bottom?
Also, I agree with double-checking the bobbin area. Loops on top mean that the bobbin is not pulling on the top thread enough. If this is not a top-loading bobbin (I don't know how to adjust those), take out the bobbin case and make sure there is no lint under the spring on the bobbin. You can run a pin underneath that spring to clear out any lint. Also make sure there is no lint around the feed dogs or anywhere in the bobbin area.
Last edited by Prism99; 02-28-2016 at 10:58 AM.