Have you read the manual and are you certain you have it threaded properly and the bobbin inserted correctly? This machine is not especially easy to thread and the bobbin needs to be going the correct way for the best tension. It's possible you are jerking and pulling on your fabric or that you now have a burr in the needle plate from breaking so many needles. If you're having the same problem on multiple machines, like you've stated, I would suggest it's not necessarily a sewing machine issue but a human being issue:> Have you taken any FMQ classes or watched some of the free YouTube videos?
Also, your local quilt shop and dealer may be able to tell you from watching you in person what's wrong.