I always have to adjust my tension from regular to FMQ. The good news is you can snip and pull the thread out of the bottom stitches and reuse your sandwich. Top tension and bobbin tension may have to be tweaked. Take a picture of your original settings so you can move them back for regular sewing before fiddling with them. I would start by tightening your top tension one number at a time and looking at the bottom after each adjustment.