Large amount of thread on rear of material, like nest

The tension on the bobbin needs to be loosened until it is loose enough to allow the thread to go through the tension spring but with a small amount of efffort. Make sure your bobbin is put in to rotate counterclockwise. Make sure you have cleaned up your feed dogs. Change your needle and you might check to see if your thread is going through the needle freely without getting jammed. All of these will prevent a problem. Anyway, try to sew. If it is a little thick on the bottom then increase your top tension. A hint is that your bottom and top thread is playing tug of war. The bottom is winning if it is too thick and vice versa. The tension on the bobbin needs to be loosened until it is loose enough to allow the thread to go through the tension spring but with a small amount of efffort. Make sure your bobbin is put in to rotate counterclockwise. Make sure you have cleaned up your feed dogs. Change your needle and you might check to see if your thread is going through the needle freely without getting jammed. All of these will prevent a problem. Anyway, try to sew. If it is a little thick on the bottom then increase your top tension. A hint is that your bottom and top thread is playing tug of war. The bottom is winning if it is too thick and vice versa.