Badly formed stitches- what am I missing?
I was given a sewing machine last week, a basic singer, and I've been trying to teach myself how to use it, but I can't seem to turn out anything except badly formed straight stitches. The thread will run straight along the top without going down through the material, and on the bottom it will be all loose. I've rethreaded it countless times, changed the needle size, adjusted the tension, sewed countless test seams, and nothing works. The cloth is 100% cotton, printed with a pattern. I'm not sure exactly what it is because it was just something I had lying around, but it doesn't stretch at all. The needles that came with the machine are brand new, so it isn't an old needle, either. However, they didn't give me anything smaller than 11/80.
Please help if you can, guys. I'm about to start banging my head against the wall.