If you like, feel free to put a pillow directly under your crotch to raise your bum slightly into the air and change the angle of entry. You should go to class more and have sex less you sounds dumb as hell. You can do that more easily when you do muff dive or when you have sex, if the positions permits. And then it will be easy for the penis to move back and forth, and it will be pleasurable. You can place a small pillow beneath your butt to lift it for anal sex. It is important to get her anus walls adjusted around invading items and especially fleshy ones, yours. I generally like side by side sex positions and my boyfriend like dogy style.