My last girlfriend before I met my wife liked her ass fucked, and often took my cock out of her pussy and stuck it in her ass, which is what you should often do. If she got me in her ass from behind when she was on her hands and knees, she would buck like a horse as I fucked her ass deep and hard, so that I had to avoid getting hit in the face with the back of her head, which soon made me cum on the back of her belly button, but personally I preferred to cum in her mouth laying there on my back watching her suck me until I cum and she swallowed it all. There are some ideas for you