Plee-
Do you start your quilting in the center of your quilt? You want to quilt in quadrants, always starting from the center and working your way outward.
Also, with just those 2 feet, you only quilt in straight lines, right? You need a darning foot to do Free Motion Quilting. If you pin a fist's width apart throughout your entire quilt, starting in the center, working to the edge, then moving to the next quadrant and doing the same until your entire quilt is pinned, you should hopefully be okay this next time. With a walking foot you want the feed dogs UP. With a darning foot to do FMQ, you want the feed dogs DOWN. Hope that helps! At least you knew to leave extra backing & batting. When I started I didn't realize I was supposed to do that & would cut everything to exactly match the front. On top of that, I didn't know to start in the middle & I spent a lot of time ripping out stitches & re-quilting the thing. Not fun!
If you need more tips, post a new thread. I'm sure the other members here can help you figure it out.