Pam, has your thread snapped off inside? That center section of the front between the thread guides comes off. Towards you and up if I remember correctly. I had a thread stuck in there once. I think it can come off the thread guides sometimes, based on things I've read in the past.
Maybe it (or you) need a break for a few. What if you shut down for a few?
On thing I have NOT had to do was to mess with the tension.