I've got to agree with most of the advise already stated.
1.Take the sandwich apart and restack making sure you stretch the fabric tight.
2. Use 505 basting spray. It's the best one I have found it works well and doesn't smell
3. Experiment with a test quilt sandwich before you continue quilting your masterpiece!!!!!
4. Increase your stitch size
5. Try decreasing your tension.
6. Use either gardening gloves or 2 pieces of the waffle shelf liner on your hands to keep a slight tension on the fabric as you feed it through the machine
7. Try a walking foot.
8. Use a topstitching needle.
Good luck it takes experimenting and patience.