So my boyfriend and I are both 18 and he has had sex before and I have not. He is 5'11" and very skinny and I am chubby, muscular and 5'7". I want to have fun things like cowgirl and reverse cowgirl in our sex life but I am posting here wondering if this will be uncomfortable for him since I way significantly heavier than him. I mean I know you aren't putting all of your weight on them but sometimes I don't know my own strength/ weight and I wouldn't want to hurt him. Any advice or tips?