Kathy - I have the same machine and it does stop and let me know when the top thread breaks or if there does not appear to be enough bobbin thread. Check page 50 of your manual where it mentions the upper thread sensor. There is an option to turn it off so perhaps your machine has it turned off.
You make the change in the machine settings.
I was having some issue with my thread breaking and I found that the way you thread through the pre tension thread guide make a difference.
I was also having some trouble with the auto needle threader almost shredding some of the threads and that was causing breaks as well.
Cathy LeBlanc Burlington MA