Clean out your bobbin area and tention area.
One time on mine there was a 1 inch piece of thread wrapped around in the tention area. I finally got a flashligh out so I could really see, and just barely saw what I thought was lint, but it was a piece of thread that was causing all the trouble.
When mine acts up, I rethread BOTH the bobbin and tention at the same time and change the needle
I know it frustrating. I feel for you.
Syl