I've been machine quilting for about 20 years.
Did you make your backing and batting about 4" larger than the top? I use curved safety pins for machine quilting, a walking or darning foot for quilting.
I lay my backing(wrong side up) out on 2 large tables and tape it to the table, so that its taut but not stretched with no bubbles. Center the backing and batting on the table and the quilt top too.
Next I lay the batting on top of the backing, smooth it out and then put the quilt top on that. Then I pin about every 4" all over the whole thing.
Sharon in Texas