I do straight line quilting with a walking foot and also FMQ all with poly batting, it's not the super puffy kind, it's the one by the warm company. I doubt it's your batting. I think if you've gone thru all the previous suggestions like new needle, rethread, etc then make some practice sandwiches out of scraps or some little baby blankets if you know anyone expecting, use the same fabric and batting types that you've been using as others suggested, and practice practice practice. I recommend a silly movie in the background or music, have a cup of tea or delicious adult beverage and have fun with it! When you feel yourself getting stressed out then it's time to take a break. Good luck!