If you are breaking needles you are pushing or pulling the sandwich enough to cause the needle to hit something or the thread path of the thread from the spool is obstructed. Make sure the thread is moving freely from the spool and not catching on the notch or edge of the spool and check the thread itself. I had a King Tut quilting thread make a little lint ball behind the needle and the needle broke from that. Completely rethread with another spool and see if that helps.
As a last resort, the timing may be off which will mean a trip to the shop.