I'm trying to do shirring? I'm using elastic thread in the bobbin and I've tried loosely and

Question

I'm using elastic thread in the bobbin and I've tried loosely and tightly winding the bobbin, but nothing seems to be working. When I put the bobbin thread in the case, it's too tight tension wise so I tried not putting it through the tension in the bobbin case. When I start doing a straight stitch the needle thread keeps getting caught around the bobbin/bobbin case? Help!