Bf and I have a decent height/size difference and a very healthy sex life, but we(mostly me) and getting really annoyed during sex when we're going at it and just sliding around everywhere. Sometimes when he's going really hard, it feels like he's just chasing my ass around on the bed. I mean I guess I can do more shoulder work at the gym to push back more, but to really be able to counter that, I'd have to look like Trogdor with 2 arms and equally scaly. Help a girl out. Was looking at the liberator throw, but it seems like it's more for squirt-proofing than slippage.

Edit: Specifically our favorite position, doggy, but bc of anatomy and what not , doggy has to be ass-up-face-down (feels like my vag is getting cheese-grated from the inside if not like this) and thus harder to prevent slippage.