it's a tension issue.
re-thread the machine, making sure you are using at least a size 14 needle. 16 would probably work best.
check the bobbin area thoroughly for lint and other shmutz.
take the bobbin case out, too, so you can check everything everywhere.
put it all back together, make sure your bobbin is going in the correct direction, and reset the tension to the factory setting. you might have to adjust it a bit from there but the other problems have to be solved first.
__________________
- necessity is the mother of invention. lazy is the crazy aunt.
