Are the eye lashes on the top or bottom? If they are on the bottom the top thread is being pulled down too far. Either the bottom tension is too tight or the top too loose. Unthread your machine, set all the tensions back to factory settings. Rethread with 2 different colours of thread and put in a scrap of your fabric in the machine. Set to zig zag stitch and work with it until you get the thread rebalanced. Once you've got it rebalanced, try a regular straight stitch.
This sounds like a silly thing but, did you make sure the foot lever was in the down position even if you are FMQ? The thread tension is not engaged if the foot is up. Good luck, the last time mine messed up it took 2 days to get it right again. I hope yours goes quicker.