intel,
try a few of these tried and true things:
When sexing her doggy style, grab her hair and pull on it, and thrust harder, faster, and deepr when you do. Bite her on the back of her neck as your pumping away.
Grab her arms and pull them behind as if she were bound.
While she's against a wall, grab her arms and pull them up, again as if she wer bound. Feel her up. Finger her. Kiss her mad pasionately,. Bite her neck. Spread her legs open and pound her into the wall.
You can also express a little aggression by varying your thrusts. Pound into her hard, and vary to soft. Put it in halfway, then slide it in all the way in.
Also, grabbing her waist, aher thighs, and flipping her around and over to accomodate the positions is tried and true too.Bascially, she wants to be Manhandled every now and then.
Also, try to look at your love making as kind of a symphony. There are a LOT of Dynamics. Loud, Soft, Fast, Slow. So think along those lines on your sex with her. Alternate positions, sometimes coitus, sometimes oral, or fingering penetration, rubbing.
You've got loads of stuff you can use to avoid a flat, boring, and predictable sex life.
Maestro!! A Crescendo, please!!