If you have a magnifying glass, use it to look for burs on the bobbin casing. Your machine came with two bobbin cases set at different tensions, one for regular sewing and one for embroidery. Make sure you are using the right one.
You may want to double check your upper thread path and the direction of your bobbin in the case. You can try threading your machine with unflavored non-waxed dental floss can help remove any dust or thread bits.

change the needle it may have a burr

New needles can have burrs but also make sure your tension has not changed. If top tension is too tight it will put up bobbin thread to surface. If top tension is too loose it can create loops on top also. Most of the time the bobbin tension is fine but the top creates the problems. I always tell a couple girls in club----if thread problems or breaks, remove the thread from top and bobbin and rethread---also their thread breaks because the threads start looping around the spool holder and they don't pay attention to that.