Having problems with thread/backstitch Sewing Machines Parts and Sales in Los Angeles

I keep having this problem: I stop sewing in a piece of fabric, I lift up the foot, but the threads seem to be stuck in the machine. Instead of one thread from the top and one from the bottom, there are 3 threads from the bottom going into the fabric. Two of these threads are “stuck” and the other one is the normal one coming from the bobbin.

If I pull hard enough on the fabric, these two stuck threads break off and the fabric is unstuck. I can’t take pictures at the moment, but it’s basically just 3 threads coming out of the bottom instead of one, and they’re stuck.

The thread seems to get stuck around the bobbin case, no idea why.

This only seems to happen when I do a backstitch when I start sewing. I also keep getting the problem where the underside of the fabric forms a “nest” of thread when I do a backstitch. I’ve tried holding the loose threads as was suggested earlier, but that doesn’t seem to work.