I am trying to get back into sewing after not having looked at my machine for 20 years. I bought a Singer 2 years ago and figured it was time to use it. My qwillow is assembled and I am trying to sew the pillow onto the quilt front. The layers are thick- cotton, flannel, and low loft batting. The problem-my bobbin thread keeps bunching up horribly. I am using a size 16 needle. There is no dirt in the bobbin case. I am using Coats and Clark thread. Is my needle size wrong? Please help if possible. My granddaughter is so excited for her qwillow :-(