I am underweight and my hip area has very less muscle, so whenever I sit on a hard surface or a surface with thin cushion, I start feeling the hardness of the surface against my bottom in seconds and the uneasiness is similar to the feeling of pressing elbow against a hard surface and consequently it becomes very difficult for me to sit on the surface. PLEASE HELP ME AS TO HOW I CAN GAIN MUSCLE IN MY HIP/BOTTOM AREA.