Don't give up!!!!! It does take a while to build up your coordination, just keep trying. You probably don't have enough pins in it. They should be about every three inches.
I find it much esier to puddle your quilt than to roll it, the rol gets too heavy, and bothers my shoulders.
There is a fab. sight to learn about machine quilting: Daystyledesigns.com. She has great suggestions. Her best suggestion is that you practice. It is the best quilting advice.