Originally Posted by
PaperPrincess
Don't know what kind of machine you have, but there is a tension spring in the bobbin case. Either it has loosened a bit and needs to be tightened or there is a bit of lint stuck in the spring causing it to be too loose. Look in your manual to find how to clean the bobbin case.
I have had the tiny pieces of thread stuck in my bobbin case more than once. Sometime they can be hard to get out but they have to come out in order to sew correctly. I have this happen on both top and front bobbin cases, by the way. On older and newer machines.