Where is your thread breaking? If it is in or around the tube of your bobbin then you may have a burr or grove in the bobbin tube. The best solution is a bobbin with either a full ceramic tube or ceramic inserts in the end(s) Most metal tubes will grove very quickly.
When your thread breaks the first thing to do is not panic. If there is a tag end of thread available put your hackle pliers on it. That will keep the wraps tight. Restart your thread, then tie down the loose end with a couple of wraps, don't try to re start and tie down at the same time. Trim out both tag ends (one from when the thread broke and one from when you restarted), and continue as normal.
Cheers,
C.