Similar to the popular Cowgirl position, you kneel on top of him, pushing off his chest and sliding up and down his thighs. But he helps by supporting some of your weight and grabbing your hips or thighs while he rises to meet each thrust.
Less stress on your legs, making climaxing easier. Plus, female-dominant positions delay his climax, so everyone wins.
Alternate between shallow and deep thrusting to stimulate different parts of the vagina.