If your stitches look loose and loopy on the bottom, or tight and puckered on top, it's almost always tension. Here's what to check first: 1. Rethread your machine completely — top thread AND bobbin. (Yes, even if you "already did it." Do it again.) 2. Make sure the presser foot is DOWN before you thread the top. If it's up, the tension discs aren't engaged, and your stitches will be a mess. 3. Test on a scrap piece of the same fabric you're using — not a random scrap. That's it. Half the "my machine is broken" moments are just this. Try it and come back and tell me — did your stitches clean up?