Every time I have sex with a guy I feel like he doesn't do it right or either the position doesn't work as well for me because I keep getting these really weird bruises at the end or sheer pain in my pelvic bones. I tried lying down flat on the floor and did some yoga exercises to stretch my bones and flex to further relax my muscles but during sex, it takes so much effort it makes me so tired. Is it normal and is sex generally a very difficult activity or is it just my lack of stamina speaking for my laziness and my inability to consistently have sex with my partner without taking breaks?