How do you sew using a mannequin?

I love to sew, but I dont like using patterns. I dont know why. But I have a dressmakers mannequin, so I use that and I draw out my own patterns. But how do you use a mannequin to sew? I either get it stuck on the mannequin so it cant come off or somehow it does not fit me in certain places. I thought using a mannequin would allow me to make the perfect size, but maybe I am just not getting exactly how to use it. I have to take the outfit off of it everytime I want to sew (to use the machine) so it feels like it is almost pointless. PLEASE HELP! I would love to make things fit properly, I love design!