To adjust your tension, first get the bobbin tension right by doing a "drop test". Tiny changes until the bobbin case gently drops when held up a few inches from your hand. Only then do you adjust your top tension appropriately. And I do agree with ManiacQuilter2 that some of the issue may be in your hand movement. Even if you think you are moving your fabric consistently, you might be moving a little faster on curves leading to "eyelashing" on the back (which can look like a tension issue).