sewing projects can be like that. I sympathize. You can definately pick it out and redo it. My first PUL diaper got resewn about 4-5 times on the one leg casing. Combination of my sewing machine going nuts and not having any experience with PUL. I did get it finished though and the pin holes totally sealed after a hot wash and dry. Definately pin or clip or something to keep your layers together when you're sewing and also try sewing with the PUL down (towards the feed dogs, not right against the foot) go slowly. You can do it. It WILL work when you're done and after the first one or 2 you'll be sewing them like a pro!
Remember too, while it's a bit of a pain to get PUL, it's actually a very reasonably priced fabric.