The thread on the bottom bunches up all down at the bottom than bunches up
Usually problems like this are caused by improper bobbin winding and installation, incorrect tension, the wrong needle for project, or simply not grasping the threads and gently pulling them backwards when you start a seam.
1. Make sure you are threading the machine correctly.
2. Check your tension.
3. Check the bobbin, make sure it's wound properly and that you don't have the bobbin in upside down.
4. Check for bits of fluff and thread in the bobbin race area.
5. Change your needle, they wear out, get bent, dull... etc. You should have several different types on hand at all times.
6. Grasp both the threads gently and pull slightly backwards when you begin a seam. this will assure that your bobbin thread doesn't get all bunched up under the fabric.
7. Always test tension, needles etc., on a scrap piece of fabric before you begin sewing your project.
:o) Smile... sewing is fun... remember?