Spandex is a bit more difficult to sew than standard non-stretch ("static") materials. When cutting the pattern and sewing seams in spandex, always be careful to ensure that the fabric isn't stretching (and thus distorting its shape) while you are working with it. Layers of spandex can be difficult to cut because it is slippery. The best way I've found is to use a rotary blade cutter and mat. You can find these at most any fabric store. The cutter works like a utility knife that has a round, rotating blade. It makes cutting curves a breeze and you can use a ruler to guide straight cuts. The mat is plastic and it "self-heals" cuts so they don't show. In order to properly sew seams in spandex, you need a serger. This is a special type of sewing machine which sews edges together using multiple threads; the result is a seam that can stretch with the fabric. It is possible to sew spandex using a standard sewing machine, instead. Use a zig-zag stitch in order to get a good hold on the spandex, so that the seam's tensions aren't pulling along a single line. This seam will adequately hold the spandex, but it won't have the same stretchy properties. The best way to start a stitch is to put the fabric under the presser foot and lower it. Next stitch just 3 or 4 stitches with the foot pedal or by rolling the handwheel. This secures the thread to the fabric. Then you can pull the loose thread ends to help feed the fabric through.

In addition to the above post, try wooly nylon threads that stretch with the fabric & use a serger with a ballpoint needle