Sewing Lycra Fabric?

Well, it sounds like you've already cut it out and have started to sew and you're having problems with the neckline. Try zigzag stitching 3/8" or 5/8" clear elastic to the raw edge of the fabric and then turning it in to the wrong side and top-stitching with a double needle. Then steam lightly to embed thread to fabric. Always sew slinky seams with a medium length narrow zigzag stitch or double needles.

I've encountered that problem from time to time too. What I've learned is that you need to use a "ball point" tip needle in your machine and also use ball point tip pins when working with this type of fabric. I use tissue paper (the kind used to wrap gifts or stuff gift bags) and pin the fabric between two sheets. Make sure the fabric is lying flat, then pin securely. I usually take a pencil and draw the line I need to stitch directly on the tissue paper.