craftgrrl | Sewing Machine Question

I've been getting really crafty lately with my sewing machine and have run into a problem maybe you know something about.

While sewing, everything is set up the right way, suddenly the top bobbin will be pulled very hard like a yank in the thread and normally the thread will snap but I've gotten some very durable stuff that isn't breaking as easily.

Underneath the fabric when I take it off of the machine and turn it over, there is almost a rats nest of thread tangled up underneath. The bobbin is in correctly and I'm not sure how to do the tension so it's probably at a 2 (I'm assuming this is okay). The stitch length and width is also set about a 2. I've used those settings for a really long time and it was fine beforehand.

Do you know what that could be? I'd love to finish up these projects for work and would have to take it back in for another $100 or so service. I did that a couple of years back for the same thing and it worked again for a while. Does that sound like an oil issue? I've never oiled it before and someone mentioned it to me earlier today.