I have been FMQ for a few months so am still learning also. One thing that worked for me may help you depending on the type of bobbin your machine uses. Mine is metal with the little finger that sticks up, pointing toward one side, it has a tiny hole at the end of the finger. If I thread the bobbin thread thru that hole the underside stitch looks so much more even, it changes the tension in some way that works. There are many kinds of bobbins so won't work for all machines, I have a Bernina 930, wonderful machine, had mine since 1986 and still going strong. Keep trying, it will get better with practice!