is the thread snagging on anything? can you sew a straight line without it breaking?
take out the bobbin, and clean the area out..oil it if you have the wick in the bobbin holder, just a drop.
by chance is the spool on right? it's not catching on the little notched out part on the bottom? (which should be on the top,so you just flip the spool around. )
widh i was there to help..